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Every precision shooter wants consistency, but powder temperature sensitivity can introduce a variable that many overlook. As outside air temperatures rise or fall, a powder’s burn rate changes, altering muzzle velocity and shifting a bullet’s point of impact. Some powders are less affected by swings in temperature than others, but many introduce enough variation to cause a miss – especially at extended distances.
This article will dive into:
- Advice from ballisticians and industry experts on powder temperature sensitivity
- Quantify what that means in the real world
- Share first-hand test results of the most popular powders
- Itemize a list of some of the most temperature-stable rifle powders
My last article shared load development tips from Jeff Siewert, a ballistic engineer with 40 years of industry experience. Jeff explained that the specific powder we choose has a direct impact on the size of our groups. Some powders are much better than others in terms of maximizing the precision of your rifle.
Jeff’s last point when it came to choosing the optimal powder for extreme precision was this: “The propellant has a low temperature coefficient; its performance is not overly sensitive to increases or decreases in ambient temperature.”
All powders will change to some degree based on the ambient temperature of the powder, but some are far more sensitive than others.
“As a long-range shooter and precision rifle competitor, temperature sensitivity is something we all need to be knowledgeable of and at varying degrees concerned with. There are instances you can get away with a lot of things and not have any concern, not even knowing it exists, but there are also times when, if you don’t account for it, you start stretching the legs on what you’re shooting you’re going to miss the target simply because of the temperature sensitivity of the propellant.” – Seth Swerczek, Hornady Marketing Communications Manager
Handloader Magazine published this powder temperature sensitivity chart, which shows what they’ve measured over the years in terms of variance in velocity with the same load at different temperatures. For one load, they found an increase of 87 fps from the load being at 70° to 115° F! That is an increase of 1.9 fps per degree change!
Legendary sniper trainer Todd Hodnett said they measured some ammo made for the military that used Alliant Reloder 15 powder and it varied by 160 fps from 40° to 140° F! They switched to ammo that used IMR 4064 powder, and saw only 60 fps swing over that same 100 degree swing. Todd did that same test with H1000 in a different cartridge, and saw virtually no change over that same range. (View video where Todd explained all that.)
So there are popular powders out there which can vary up to 1.5-2.0 fps per degree. But what would that mean on a target? How much does it really matter?
Real-World Example of How Much Powder Temperature Sensitivity Matters
Let’s say a match started at 40° F and climbed to 80° by afternoon (common in west Texas, where I live). We’ll use the 1.9 fps per degree difference that Handloader Magazine reported. Let’s say our muzzle velocity started at 2800 fps on Stage 1, but as the temperature rose to 80°, our MV climbed to 2876 by the last stage. If our elevation adjustment on a target at 1000 yards was perfectly centered when we started – we’d be hitting over 20” higher by the time we finished! We aren’t shooting 4-foot-tall targets in matches, so you could see how even a fraction of that temperature sensitivity could put you off the plate. In fact, it would only take a 37 fps increase over that 40-degree swing, and it would likely cause us to miss a 20” tall target at 1000 yards.
The example above assumes that everything else was perfect! You broke the shot perfectly, the range was 100% accurate, your ballistic solution was 100% accurate, your wind call was perfect, and your bullet went perfectly into the center of your group (plus lots of other things). If any of those things were off, we could end up off the plate with even less velocity change.
While we’d love to have absolutely no variation in our velocity, it seems like the practical goal for long-range shooters is that we need the variation to be less than 1 fps per degree Fahrenheit. How far under 1.0 you desire will vary from one person to another and based on the application – but we can probably all agree that 1.0 fps per degree or more is too much for precision long-range shooting.
Keep in mind that the outside temperature doesn’t have to be 115° for your ammo to reach 115°. If you leave your ammo in the sun on top of a dark surface, the ambient temperature of the powder inside the case can get there pretty quickly. After all, we aren’t talking about the ambient air temperature but the temperature of the gunpowder itself at the moment of ignition. That is often related to ambient outside air temperature, but not always.
A few months ago, Hornady published a 1-hour podcast focused on powder temperature sensitivity. Their hopes were to make it easier to understand, calculate, and account for. I will share a few highlights, but certianly won’t cover everything they did – so I’d suggest you watch that if you’re interested in the topic.
I’ll share a few highlights from the podcast that stood out to me. For context, Jayden Quinlan is the senior ballistician at Hornady, and he is often brought in on the more technical podcasts like this as a subject matter expert.
Seth: “In a given propellant, let’s say you got a cartridge like a 300 Win Mag, and the same propellant also works in a 6.5 Creedmoor or a 270 or something like that. Does the cartridge volume play into the sensitivity of a particular propellant?”
Jayden: “Yes. Absolutely.”
Seth: “That’s an important note because I feel like there are a lot of powders out there that people go, ‘Oh, I’m using Varget, so temperature stability is like 0.2 or 0.3 feet per second per degree. I don’t need to worry about it.’ But the problem is they’re going off anecdotal data, and depending on their individual cartridge volume, it could actually be maybe better or worse than what they thought.”
Miles Neville was also on this podcast, and he is a project manager at Hornady who works alongside Jayden. Miles has tested temperature sensitivity first-hand in their lab for a lot of different types of powders, cartridges, and loads. Miles also happens to be one of the pro shooters in the Precision Rifle Series, finishing 2nd overall in 2023 in the PRS Gas Gun Division and 101st in 2024 in the PRS Open Division. Here is something Miles said in the podcast that caught my attention:
“Even if a guy wants to be really picky and only use the good powders that are known to be insensitive to temperature like H4350, Varget, others in the Hodgdon Extreme line, or some of the Alliant powders that are really good – you can still see it. If you are going to be zeroing and setting things up at 70° F and then using that ammo below zero or when there are 50° or more difference – you are going to see the effects of that. It’s less common that people notice it because, for the most part, people don’t want to go out and shoot a match when it’s freezing – although some still do it. There is a creep in velocity, but some people may not notice it.” – Miles Neville
While I’ve known about powder temperature sensitivity for years, I am also a shooter who exclusively uses Hodgdon Extreme Series powders (primarily Varget, H4350, and H1000). To be clear, I’m not sponsored by Hodgdon (or anyone) – that choice is simply based on lots of experience and wanting to avoid the whole temperature sensitivity issue. But that means I’m pretty much the guy that the Hornady guys were talking about that was dismissing it because I was using Varget or another powder that is known to be less sensitive to swings in temperature. Those guys have tested more ammo than just about anyone – so it caused me to wonder if I might be glossing over something that I need to account for.
It is fairly rare for me to have elevation issues (i.e., miss a target high or low). Like other pro shooters, I verify that my dope is lining up with my Kestrel ballistic calculator before every major match. But, even if it is rare, we do all occasionally miss a target high or low. Could temperature sensitivity be one of the contributing factors?
PRB’s Powder Temperature Sensitivity Field Test
I couldn’t shake that question from my brain, so I eventually had to test it for myself! Miles also mentioned a powder’s temperature sensitivity “is almost never linear from ambient to cold or ambient to hot.” So, I knew that I wanted to not just test two extremes and assume it would be linear between those two data points.
Jeff’s comments made me think I should test at the most extreme low temp I could see myself shooting in, which I thought would be close to 0° F. I also thought I should test just above freezing because the trend in velocity might vary as it crosses that crystalline threshold.
I ended up loading up 10 rounds to test around these temperatures:
- 5° F (Freezer)
- 33° F (Refrigerator)
- 58° F (Cold room)
- 76° F (Warm room)
- 108° F (Warming blanket)
I tested my 6mm Dasher match ammo that has Varget powder, and I also tested my 6mm Creedmoor match ammo that has H4350 powder. I fired 10 shots of each type of ammo at each temperature in my 100-yard underground tunnel. On the Hornady podcast, they mentioned that powder temperature sensitivity might not just change your velocity but could change your point of impact. So, I wanted to quantify any POI shift as well as measure the velocity over all those temperatures.
For each temperature, I wrapped the ammo in a towel with a Kestrel that was set to log the temperature every 2 minutes. Then, I put it in an environment that would acclimate it to the desired temperature range and left it for 8 hours. A study published in 2022 by the Journal of Ballistics investigated the temperature equilibration times of various ammunition calibers under different heating/cooling conditions. The study found “the equilibration time of the small-caliber ammunition is only 7-8 hours.” Once I pulled the ammo from the environment, I’d log the average temperature the Kestrel measured over the past hour, take the ammo to my tunnel, and shoot it immediately. Then, I’d let the barrel of the rifle cool to ambient temperature and repeat for the next set of ammo.
In full transparency, I measured the 76° batch first as the baseline – and I accidentally skewed those velocity measurements. So, I had to toss out that data, but I have 100% confidence in all the other data. And we’ll see in the data, that extra data-point wasn’t necessary to clearly see the pattern.
Powder Temperature Sensitivity Test for Varget in my 6 Dasher
So, after carefully firing 100 rounds of ammo at a wide range of temperatures, here is what I found:
For the 6mm Dasher with ammo using Varget powder, I measured an average velocity over 10 rounds at 5° F of 2,821 fps, and at 108° F, the average was 2,835 fps. That is only a 14 fps velocity difference over a 103° temperature swing! That averages a 0.136 fps increase per degree over that range. You can see there was close to 0.2 fps per degree between 5° and 33°, but then only 0.1 fps per degree from 58° to 108°.
To put that into context, at 1000 yards that 14 fps difference would result in 3.75” of elevation error! So as long as I’m not shooting at a targets smaller than 8” tall at 1000 yards, it isn’t enough to result in a miss – even if my ammo temp 103°! The truth is, it would be a very extreme example for us to even see half of that swing.
Did I see any point of impact shift? Nope. That tiny change in velocity was not enough to cause any POI shift. But, here is the target I carefully measured to prove that was true. I fired 10 rounds at each temperature but split them into two 5-shot groups.
(Fun Fact: My average 5-shot group over all 10 groups measured 0.298 MOA! Thanks to TS Customs for chambering some impressive barrels from CRB! And no, I’m not sponsored by any of them.)
So, with the lot of Varget rifle powder that I’m currently loading out of my 6mm Dasher, I feel like I can safely ignore any effect of ambient temperature swings.
Powder Temperature Sensitivity Test for H4350 in my 6mm Creedmoor
But what about the 6mm Creedmoor with the H4350 load? Here are the results for it:
It also showed very little temperature sensitivity. My average velocity was 3,088 fps at 5° and 3,102 fps at 105°. So we had a 14 fps increase over 100°, which is exactly 0.140 fps per degree. Funny enough, that is almost identical to what I measured for Varget! I was shocked they were so similar.
In the case of H4350, there wasn’t as much change from 5° to 35°. We saw 0.19 fps per degree with Varget in that coldest window but only 0.09 fps per degree with H4350. At least according to some forums, H4350 is a single-base powder, while Varget is a double-base powder. So maybe that makes sense – or maybe it’s a coincidence.
Once again, with just a 14 fps difference in velocity over a 100° swing – temperature sensitivity for my lot of H4350 powder from my 6mm Creedmoor seems to be in the noise for all practical purposes.
As I said at the start, while we’d love for the difference in muzzle velocity to be 0 fps over 100° – for practical purposes, it would take a closer to a 40 fps swing in my rifles to be the leading cause of missing a 20” target at 1,000 yards. I’d say the largest swing in temperature you might see in a single day might be 40°. So even if we had up to 1 fps per degree, it would put the shot off center but may not result in a miss.
Now, I’m not saying I’d be satisfied with that because it assumes your wind call was perfect, and you hit the very top or bottom of the plate. I prefer to stay more centered in the plate (as we all do) to leave myself a little more margin for aiming error, so I would probably be concerned with anything that showed 0.5 fps per degree or more. But, at least in my testing – Varget and H4350 were well below that threshold of being meaningful at 0.14 fps per degree.
That is a big reason why Varget and H4350 in the Hodgdon Extreme Series are the two favorite powders among the pros! 87% of the top 200 ranked shooters in the Precision Rifle Series (PRS) are using either Varget or H4350 in their match ammo (see all the data).
Please don’t let this convince you that you shouldn’t worry about this for other types of powders. There are absolutely some powders that cause shooters to start missing as the day warms up. I’ve seen it countless at matches! It used to be very prevalent, but over the last few years, several powder options have been introduced that are very temperature stable. My advice would be to use one of those two, but also test it yourself! That is the only way to know for sure.
The Best Rifle Powders For Low-Temperature Sensitivity
Finally, let’s talk about what powders are the least sensitive to swings in temperature.
In general, single-base powders are less sensitive to temperature variations compared to double-base powders. Single-base powders contain only nitrocellulose, making them more temperature stable and ideal for precision shooting, while double-base powders include both nitrocellulose and nitroglycerin, providing higher energy but often increasing temperature sensitivity. Double-base powders are commonly used in magnum cartridges and military applications, whereas single-base powders are preferred for long-range consistency.
In the book Ammunition, Demystified, ballistic engineer Jeff Siewert went even deeper: “Propellants containing nitroglycerine (e.g., double-base or triple-base chemistries) have a reputation for sensitivity to cold-temperature conditions due to the crystalline transition temperature of nitroglycerine being just 15-20° C above the typical -40° C typically specified for operation of military propellants. Below this temperature, the grain can fracture in uncontrolled ways, causing a rapid increase in the burning area of the propellant and a resulting spike in peak pressure.” Jayden Quinlan, senior ballistician at Hornady, mentioned that same phenomenon on the Hornady podcast. (Note: We don’t use triple-base powders in small arms, so that isn’t relevant here.)
Now, that doesn’t mean that ALL double-base powders are highly sensitive to temperature or that all single-base powders are NOT sensitive to temperature. There are a number of techniques manufacturers use to try to mitigate this kind of temperature sensitivity, so unfortunately, it isn’t as easy as saying, “Single-base is always good, and double-base is always bad.” However, it is true that single-base powders are usually more stable across different temperatures, which makes them the preferred choice among many precision rifle shooters.
The Hornady team wrapped up the podcast with this million-dollar question:
Seth: “So you guys have done a bunch of testing. In the world of precision rifles, what are a couple of the best powders you’ve ever tested?”
Jayden: “The Hodgdon Extreme Series has the longest and best reputation. That is powders like H4350, Varget, H4381, H1000, Retumbo. The temperature stable series from Alliant is amazing and has had some of the lowest temperature sensitivity factors that I’ve ever seen – like zero!
Seth: “Those are propellants like Reloader 16, 23, 26, and 15.5. When Reloader 16, 23, and 26 first came out, I thought we were doing tests wrong! I thought, ‘Wait, this isn’t how it is supposed to work!’ It was especially surprising for some of those big charge weights, like a 300 PRC with 74 grains of Reloader 26 powder in there. You think there is going to be a pretty significant shift with temperature, but some of that stuff just didn’t budge.”
Jayden: “Then in some of the newer powders, the Winchester StaBall 6.5, StaBall HD, and StaBall Match – those 3 are very temperature stable.”
Miles: “Yeah, the StaBall HD and StaBall Match are more temperature stable than the StaBall 6.5. But again, in that Winchester StaBall family of powders, we’ve seen some that are effectively no change in velocity from -20° up to 140°. You are talking single-digit foot-per-second deltas from coldest to hottest, which is crazy. We’re used to seeing how many tens of feet per second it is going to be different – and then you see nothing. Wow! Okay!”
So, after years of extensive testing with an wide range of powders, cartridges, and loads, here are the rifle reloading powders that stuck out to Hornady engineers as being the least sensitive to swings in temperature:
- Hodgdon Extreme Series Powders, which includes H4350, Varget, H4381, H1000, Retumbo, H4381SC, H4895, H322, H4198
- Alliant Reloder Temperature Stable Series Powders, which includes Reloder 16, 23, 26, and 15.5.
- Winchester StaBall 6.5, StaBall HD, and StaBall Match
The Bad News About Alliant Reloder Powders
Unfortunately, in May 2024, Vista Outdoors (the company that bought Alliant Powders in 2015) posted this:
“Due to the worldwide shortage of nitrocellulose, the Vista Outdoor supply agreement for the sale of Alliant Powder canisters has been suspended for an unknown period. At this time, we have no timeline for the fulfillment and will be canceling outstanding Alliant orders in our system. Representatives will provide updates and coordinate new orders based on availability.”
So Alliant Reloder powders have suspended sales to the public indefinitely. There may be military or commercial ammo manufacturers still using it, but it’s not available for us reloaders for now. Hopefully, they will be again at some point in the future.
The Take-Away
Temperature sensitivity in rifle powders is a real factor that can cause measurable shifts in velocity, and in extreme cases, it could mean the difference between hitting and missing a long-range target. While some powders exhibit significant changes in muzzle velocity across temperature swings, my testing of Varget and H4350 showed that they remained impressively stable—averaging just 0.14 fps per degree of temperature change. This confirms why these powders dominate among top PRS shooters. If you’re serious about precision shooting, choosing a temperature-stable powder is essential, but as always, the best approach is to test your specific load to ensure confidence in real-world conditions.
Coming Up Next
This article is part of a series on rifle reloading data, load development, and reloading components. Here are other related articles that I’ve recently published or plan to publish in the near future:
- Best Reloading Presses & Dies – What The Pros Use
- Best Powder Scale – What The Pros Use
- How Do The Best Shooters Reload? What The Pros Use (This is all about the reloading steps and process that these shooters perform to reload their match ammo.)
- Best Brass – What The Pros Use
- Best Long Range Bullet – What The Pros Use
- Unlock the Secrets of Ammo: A Must-Read for Every Shooter and Reloader (This is a review of the book Ammunition, Demystified by Jeff Siewert, which is the best book I’ve ever read on ammo.)
- Best Rifle Powder – What The Pros Use
- Rifle Load Development – How To Pick The Right Powder & Load
- Powder Temperature Sensitivity – Why It Matters & Best Powders To Use
- Best Rifle Primers – What The Pros Use (coming soon)
- Best Match Ammo Options For Shooters Who Don’t Reload (coming soon)
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Excellent topic and excellent research, as per usual. Very relevant and informative. Thanks for doing it!
I have seen small increases of a few fps in velocity when going from 26 or 27°F down to below 0°. While it’s probably a result of my poor reloading I wondered if perhaps my chronograph would give inaccurate readings in subfreezing temperatures (before it froze and quit working.)
You freezing the ammo and not the chronograph seems like a much better way to test velocity.
Hey, Rodney. Thanks! Glad you enjoyed the content! Honestly, I was expecting to see way more variance than I did. It was pretty surprising to me. But, anytime you do a real-world test … you’ll likely uncover at least something that surprises you. That’s why it’s fun to tinker with stuff like this.
That’s a good question about the chronograph. I actually don’t know enough about how each chronograph works anymore to have an intelligent guess. It seems like chronograph design has gone into some pretty advanced fields in recent years with magnetic fields and radars. I would expect that they’d have a wide operating range in terms of temperature, but I wouldn’t be surprised if that didn’t vary based on which chronograph you’re using.
Sorry I couldn’t be more help!
Thanks,
Cal
Question, my ballistic calculators ask for temp. Am I wrong in assuming that they calculate the temp effect on powder and adjust the holds
Hey, Bob. That’s a good question. Many ballistic calculators allow you to enter a temperature along with the muzzle velocity, but those typically require you to enter at least two sets of temp/velocities for it to be able to calculate and adjust for it automatically. For example, you could enter at 30 degrees your velocity was 3,000 fps and at 80 degrees it was 3,100 fps. With those two sets of values, it could do the math and know your powder varies by 2 fps per degree. So if one day you were shooting and the outside temp was 90 degrees, it could guess that your velocity would be 3120 fps.
As I mentioned in the article, the rate at which the burn rate changes is not always linear, but some calculators I’ve seen allow you to put in several different pairs of values. So you could potentially put in all 5 of the different temperatures and velocities that I tested.
If you are only entering one velocity, which is what I’d bet is the most common use case, then there isn’t any way for it to account for the temperature sensitivity, because it wouldn’t know how to guess at how it would vary based on the ambient temperature.
I personally don’t enter the table values, because I feel like you could be overfitting your model … and just because the ambient temperature is 40 degrees doesn’t mean that my powder temperature is 40 degrees. For example, when I travel to a big match, I take my ammo into the hotel with me. If the outside temperature was 40 degrees when the match started, the ambient temperature of my powder is probably closer to 70 degrees than 40 degrees. It takes a few hours for the powder inside your ammo to acclimate and reach equilibrium with the outside air temperature. By stage 4 or 5 a few hours have passed since my ammo has been outside, so it is no longer 70 degrees … but the outside air temperature has also risen to maybe 50 degrees. So my powder temperature might be 55 degrees, and might not even get down to that before it starts rising again as the day heats up.
In that case, if I had in my table that at 40 degrees my velocity is 2800 … then when my Kestrel measures the outside air temperature it is going to assume that my powder temperature is exactly the same. I think that is a big assumption. And if the temperature was even more extreme, like 20 degrees or 100 degrees … then the difference could introduce more error than it would it be helping.
I’m not saying not to use it. Obviously that is the specific use case that it was created for. But I personally don’t use it because of what I just explained. If I was using a more temperature sensitive powder, then maybe I’d use it. But honestly … I’d probably just switch powders. There are so many variables in long range shooting that we have to manage, I simply want to eliminate any of them that I can … and there are good powders out there that basically allow you to safely ignore it. So that’s my strategy. Life is too short to use powders that aren’t temperature stable! 😉
I do feel like that is a hard-earned lesson. I still see shooters at matches where their ballistics were dead on early in the day, but they start to trend high as the day heats up. I’ve even asked what powder they were using, and I’m 99% sure this is the root of some of their issues. Not everyone wants to hear that, so I don’t always offer it. We shooters can be pretty sensitive about someone telling us we picked the wrong powder for some reason. But, that is the motivation behind me wanting to write about this. I want to help those guys, and maybe some of them will read the article and notice that what I described matches their symptoms. After all, I’m just trying to help fellow shooters. This is one of those gotchas that afflicts some people and they never know it. It can sure be frustrating to diagnose, too.
I hope that’s helpful! Probably way more than you wanted to know, but I thought it might help others reading the comments. I almost put all that in the article, but it was already getting so long. Nobody ever accused me of being too brief! 😉
Thanks,
Cal
Hey Cal, You know the difference in air temperature causes differences in air density. That`s why a bullet will fly faster when it`s hot outside, as compared to when it is cold outside. I always thought that air density was the elephant in the room when figuring ballistics. Everything else is just a mouse.
Boyd
Thanks, Boyd. Yes, that does impact the bullet flight. But, ballistic calculators like the Kestrel gives you a way to enter a MV Temp table that is to help with the initial muzzle velocity. It has nothing to do with the flight or drag of the bullet … or air density. Every ballistic calculator has to account for air density, but what I’m referring to (and was referring to in other comments) has to do with the ambient temperature of the ammo itself. Here is a video where Todd Hodnett, a world-renown special forces sniper trainer, explains it all:
https://www.youtube.com/watch?v=wClM0Ll7JA8
Todd mentions that they’d seen 160 fps over a 100 degree swing for Alliant Reloder 15 powder (40 degrees to 140 degrees) … which would be a horrible miss. They switched to IMR 4064 and saw only 60 fps swing over that same 100 degree swing. He said he’d also tried H1000, and didn’t see any change over that same range.
So the MV Temp Table feature in the Kestrel is designed to help you manage your temperature sensitivity in your ammo.
Thanks,
Cal
I know this article is getting long in the tooth, but I did not know about the Kestrel input for powder temps. That is getting into Internal Ballistics, rather than External.
Thanks Cal. For some reason, your reply went to spam and I just found it.
Yes, sir! That 100% has to do with internal ballistics, but it plays into the initial launch conditions for the external ballistics portion … so the Applied Ballistics guys talked Kestrel into including it, because they wanted their engine to be able to account for it.
Thanks,
Cal
Hey Bob, The reason your ballistic calculator asks for temperature is to compensate for air density. High temp. lower density, faster bullet. Low temp, higher density, slower bullet. As Cal demonstrated with temperature insensitive powders, the effect of temperature on your muzzle velocity is practically nil. Hope that helps.
Boyd
One big flaw I see in your testing is that if the ammo is at zero degrees so will the rifle,its barrel and chamber. Same thing at 100 degrees.
Also I’m sure that as the chamber warms up after each shot that some of that temperature will get into the next cartridge.
Mal
Hey, Mal. I think it was Hornady that did experiments where they basically froze the ammo OR froze the gun OR they froze both of them – and it turned out just freezing the ammo produced the same results as freezing the gun and ammo. I’ve been reading a lot about this lately, so it may have been in Jeff’s book or another study I read – but I think it may have been Jayden from Hornady that I heard say that.
And you’re right about heat transfer from the chamber, but I believe you’re overestimating how quickly the heat transfer takes place. I didn’t leave any round in the chamber for more than a second or two. I got on target before I closed the bolt. It takes longer than that for the chamber heat to transfer to the powder in any meaningful way.
The good news is … even if those things mattered and you doubled the variance I measured, it still isn’t meaningful. So I’m satisfied that I can safely ignore this with my powders. But, if you repeat the experiment and account for those things, I’d love to see your results.
Thanks,
Cal
Two points are noteworthy in my opinion:
1) “The truth is, it would be a very extreme example for us to even see half of that swing.”
2) There is an assumption that pervades this work by everyone I have ever seen undertake it, that, based on my personal experience, is unfounded. Specifically, that assumption is that the response of gun powder ignition and burning is linear with temperature. Chemically speaking, that would be “strange”.
Excellent experiment. I appreciate the attention to detail.
Thanks for sharing your thoughts, Paul. I do think those are big takeaways, too. It kind of makes me want to repeat the experiment with one of the powders that is known to be very sensitive to temperature, but then that would mean I’d have to guy buy some of that powder … and I’m not sure I can bring myself to do that. 😉 I definitely know my experimental results with Varget and H4350 represent best-in-class temperature stability. I’m not saying there aren’t others that would be just as good or maybe even mathematically “better” (although I’d question if any improvement has practical value or if you’d even notice it at 1000 yards) … but there are certainly MANY powders that are worse than the tiny variation my experiment revealed. I think if I tested some of the powders that have more variance, we’d see exactly what you are referring to where the change in velocity isn’t linear across the entire temperature range. I think that might be especially true for double-base powders, because of some of the things that Jeff mentions in the book.
Maybe one day I’ll test a wide range of powders at different temperatures and different humidity. I’ll be honest, I was looking at some professional-grade Enivornmental Test Chambers last night! Those allow you to dial in a specific temperature AND humidity over a very wide range. It would sure be neat to have one of those, but unfortunately they seem to be $10,000+. Even the used ones are ridiculously priced! Honestly, I should probably just keep using Varget and H4350 and forget about it, but who knows! 😉
Thanks for taking the time to voice your thoughts and share the encouragement!
Cal
Any thoughts on VV powders like N140, N555, etc?
Hey, Corey. I don’t have any experience with Vhitavhori powders, but another shooter chimed in and said the VV N555 was another powder that was very temperature stable. They said they’ve done 1000s of rounds in temperature testing, so it seems like more than just one person’s opinion.
Thanks,
Cal
Hey Cal, Back in 2010, I built an M40/A5 clone with a long action R700 receiver that had a very low 5 digit number. Using a Rock Creek barrel with 5R rifling at 26″. I also bought 1000 new Winchester cases, I have only used 500 of them. They have 8 reloads each, neck sized only. I wanted the 11.27 twist for 175gr SMK`s. I used the Hornady manual and ended up with the max charge compressed of 59 gr of H4350 to get Consistent 3/8 to 1/4 MOA groups at 100 yards. I worked this load up during the summer when we had a month of 99 degree days, of course I was in the shade of some Pecan trees. But I didn`t let the barrel cool during 10 round shot strings. Didn`t measure any velocities until I had reached the precision I was looking for. Then I measure them for my ballistics. My average out of that barrel was 2955fps with an SD of 2. Later that winter in 30 degree temps, I was shooting 1/2″ low at 500yrds. Out of curiosity, I sectioned a couple of randomly chosen cases to check for thinning at the base, they were perfect. With neck sizing only, I only have to trim about every 4th reload a few thousandths. I consistently get 4″ groups at 1,000 on a calm day using H4350 Extreme, I also use Wolf LR primers, of which I bought 100,000 when I heard they were stopping primer sales. I don`t compete, I compete only against myself. But I know what to expect when I pull this rifle and ammo out of the safe. Great barrel, 4,000+ rds and only .020″ setback on the lands so far. Which doesn`t bother the SMK`s. So impressed with the barrel, I bought an extra blank within a year, still have it. Mike Rock personally handlapped both before he retired.
Boyd
Dang, Boyd! That is the kind of performance that we all hope for when we’re doing load development. It is sure satisfying when you get a rifle to perform like that. I do think the barrel has sooo much to do with it. I have had 3 “hummer” barrels like that in my 6mm competition rifles. I had one that was chambered in 6XC years ago (Hawk Hill barrel a Benchrest friend chambered) and I’ve had two in 6mm Dasher more recently (1 Bartlein from Walls Rifles and 1 CRB barrel from TS Customs). Honestly, the best barrel I’ve ever owned is a 338 Lapua that Surgeon Rifles chambered and it was a Krieger barrel. And I’ve had really good barrels from a few other barrel brands and gunsmiths, but every now and then you come across one that is really special. With that 338 Lapua, I feel like it literally shoots better than I really am. I have so much confidence in it! I’ve joked with some of my friends that I feel like I could point that rifle in the other direction and the bullet would still find its way to the target! 😉 I’ve literally drawn a smiley face on a target at over 1400 yards with it, and had first round hits in competition out to 2640 yards with it. I still have it, but honestly don’t shoot it much … because I’m wanting save the barrel life!
It does make me wonder what makes those rifles shoot so well. I do think a big part of it is the barrel. Jeff says in the Ammunition Demystified book that there are no straight barrels, but maybe those were more straight and maybe they reduced the angular momentum on the bullet when it’s leaving the muzzle? Jeff said, “The initial angular rate (w) at muzzle exit is responsible for the majority of short-range dispersion exhibited by small caliber projectiles. The interaction between the flexible projectile and the flexible, non-straight barrel bore is the source of the projectile initial angular rate.” So maybe if those barrels were straighter than normal, and that is part of it … but who knows! What I know for sure, is when you get a rifle that shoots like what you’re talking about … it is one of the most satisfying feelings in the world! It gives you sooo much confidence anytime you pull it from the safe.
Thanks for sharing your experience! Made me reminisce about the handful of great barrels I’ve had over the years.
Cal
Cal, I forgot to mention that my rifle is chambered in 30.06. I was an avid fan of German Salazar who had a blog “The .30 Cal Rifleman”. He was great shooter who loved the .06. One reason I mentioned the Wolf primers, was that he had a friend Engineer at the Air Force Academy who conducted very precise and controlled experiments on primer of all the brands, measuring flame size, length, and consistency. The Wolf primers far out did even the best and most expensive in consistency with a just under mid size flame, and Wolf primers were half the price of American primers! David Tubbs is said to have bought 700,000 when he heard they were getting out of the primer business. Salazar preferred the 175 gr SMK, having tried several more expensive ones, for his across the course 600yd and 1,000yd competition. He also had a special reamer made by PTG with a 1 1/2 degree lead angle, as compared to the normal 3 degree lead for the 30.06. I have that reamer for my extra barrel. I have also had great success with 190gr SMK`s using H4350, I forget the load, but it was a compressed load too.
I enjoy reading your stuff very much, there is so much to learn and understand and you are doing a great job of showing the possibilities.
Boyd.
Cal,
VV N555 is another very stable powder. I’ve done 1000’s of rounds in temprature testing with it and many other of the VV powders. Another thing about double base powders is they can be produced with different levels of nitro and their stability can vary.
I think another inportant aspect of temprature testing that needs to be monitered is humidity level. If one powder is at 55% humidity and the other is at 27% are you really testing velocity change based on temprature? Or is it now temprature and humidity?
Rob
Hey, Rob. Thanks for sharing your experience with Vihtavuori powders. One of my close friends has been doing load development with VV powders lately, and has been wearing me out about how great it is! 😉 After this post was published yesterday, he basically thanked me for continuing to use Varget and H4350 and not publishing how good VV powders were because he wanted to still be able to find it in stock. Ha!
You’re 100% correct on the amount of nitro in double-base powders. I almost went into that, but the article was already getting so long. It certainly isn’t that as double-base powders are bad. There is more to it than that.
Your comment on humidity is a good one. I did leave a Kestrel with the rounds to log the environmental data, and I can look to see if the data is still on those.
Funny enough, right after this post went up Austin Buschman reached out to me and asked, “Have you tested powder humidity? After starting to monitor it I’d say it is by far the number one overlooked thing that affects muzzle velocity.” So you two have me thinking about it! Last night I was literally looking at Environmental Test Chambers, which are scientific devices that allow you to dial in both specific temperatures and humidity. They’re mostly $10,000+, so I probably won’t be investing in one anytime soon! 😉 That would be the ideal way to control for both.
There are other ways to test effects of powder humidity, and I’m already thinking about it. Bryan Litz also did some powder humidity tests in Modern Advancements in Long Range Shooting Volume 3. I remember he was also surprised to see how much powder humidity impacted ballistics.
I’m not sure how long it takes for humidity inside the case to reach equilibrium with the environment. I might think it would be longer than 8 hours, which is what it is for temperature. It seems like heat might be transferred more easily to the powder than humidity, but I’m guessing at that.
Like most real-world experiments, they usually make you think of more questions!
I do appreciate you sharing your thoughts! You and Buschman have me thinking! I’m not home now, but when I get home I’ll try to remember to check my Kestrels to see if I have any of the humidity data still from this experiment. I’ll share it if I do.
Thanks,
Cal
Now that someone has mentioned a variant that I have had ‘trouble’ with, or more correctly, powder density as s function of ‘moisture content’. The single quotes were added because I’m not referring to water..
Keeping this as short as possible: I do a lot of ballistic experimentation, but in the context of hunting, not professional target shooting. (I really dislike the tendency to conflate those two *very* different goals.) As such, I have something north of 50 different powders on my shelf. When I got serious about the “garbage in – garbage out” nature of QuickLOAD, (QL) I started *measuring* the density of my powders, not relying on QL’s density figures. I had some old I3031 that i used with an old recipe. It was a tried and true recipe, developed from the same lot/canister of powder. It blew primers! Sumpin’ wrong there. Sparing you all the gory details, I eventually figured out that the powder had changed density enough that what was once a ‘reasonable’ charge, became a ‘hot’ charge. (I do *not* load charges that even tiptoe around max pressure values.) While I have not verified the cause, I am convinced that the change in density was the result of “drying”.
All modern powders of which I am aware, use ether to “dry” the powder in the last step of the manufacturing process. Manufacturers off-gas the ether as long as they can afford to and to levels that have an ‘acceptably low’ affect on performance. Nevertheless, there is either left in the powder as a result of the drying process. This is the primary component of the odor that you smell when you open a *new* container of powder. If, as I had done, you take only small amounts out at a time, opening the container *frequently*, you ‘vent’ that container frequently, essentially drying it of the ether. Do this “just right”, AND keep the container for s few years, and you might very well change the density (actually, the *energy* density) sufficiently to affect pressure and muzzle velocity. I do not mention this as a safety issue!!! (VERY tired of all the-sky-is-falling Chicken Littles!) Rather I mention this in the context of “humidity” affecting MV and thereby point of impact.
If ‘you’ are one of the people that doesn’t weigh each charge, maybe this won’t matter in your reloading. However, if you do weigh every charge for every cartridge, you most certainly can get ‘anomalous results’ with powder that has “dried out” over time, (bigger issue with 8lb containers), OR when you CHANGE LOTS.
Maybe actual humidity, (water-based) is a variable to be kept un mind when looking for ‘tenths if inches’.
Very interesting. I have certainly seen muzzle velocities climb as a powder dries out. I guess if your muzzle velocity is climbing, your chamber pressure is too … so it makes sense that there could be cases where you get dangerously over pressure when a powder gets extremely dry.
Bryan Litz published some interesting data related to humidity and powders in Modern Advancements in Long Range Shooting Volume III. You might find that interesting, if you haven’t read it already.
Thanks for sharing your experience and thoughts!
Cal
Hey, Rob. When I got home I went and grabbed the 4 Kestrels that I used during this experiment. It looked like I still had data logged on 3 of the 4, so I was able to go back and see what the humidity was right before I pulled the ammo from whatever environment it was in to acclimate the temperature. So I don’t have all 5 of the temperatures, but here are the 3 I could find:
35° was 23% humidity
59° was 43% humidity
105° was 16% humidity
So they were all drier than a lot of places, but I live in west Texas which is semi-arid. So I’m not shocked by those humidities. I’m not sure how long it takes for powder to acclimate and reach equilibrium with the surrounding environment in terms of humidity. My gut is that it would take longer than temperature. I can see temperature permeating the case far easier than humidity.
I should go back and re-read Litz’s humidity test in Modern Advancements in Long Range Shooting Volume 3. It’s been a couple of years since I’ve read that, but maybe he gives some insight into that. I think he acclimated the powder before he loaded it, but I also think he talked about how it could change when you’re driving in the car and it might even be irregular (i.e., some rounds might acclimate but others might not).
Anyway, if you’ve got that book you might pull it out too. Maybe there is something in there we could learn without having to repeat the experiment ourselves! 😉
I just wanted to share the data I was able to find on my measurement devices, in case it was helpful for anyone.
Thanks,
Cal
Cal,
Just to make sure I am clear. I am not referring to the outside humidity. Like Bryan, I am referring to the humidity level of the powder as you start to load. Say you start with a fresh jug of powder and it shows 55% humidity. Months later you want to perform this test again and you check that powder and it is now reading 30%.
You get different result on your temperature test. Is the powder reacting different to the temperature soaking or is it because the powder is now drier?
When I test ammo at a requested temperature it usually requires me to soak it for 4-6 hrs and fire it within 1 minute of being removed from the Temp. chamber.
Just some thoughts.
Rob
Ah, that makes sense. Thanks for clarifying. If that is the case, all of this ammo was loaded in the same sitting with the same lot of powder. So it seems like humidity was controlled in this experiment, from that perspective.
I did soak the ammo for 8 hours, just to make sure I was past that point of equilibrium. I fired it immediately afterward. I don’t think I got it fired in 1 minute, but it was less than 5 minutes. Because I was firing groups and not just recording velocity, I shot as fast as I could without throwing a shot. I have a really stable bench setup, so it didn’t take long.
Do you think if the powder was at 20% humidity or 60% humidity before it was loaded, and then I repeated this temperature test that the results might be different? Would we see more temperature sensitivity depending on how dry the powder was?
Thanks,
Cal
Hi Rob, I’m about to develop a 7 prc load with N570. Curious to learn if you have any data? I’m in northern AZ, humidity isn’t a big factor, but ambient temp and elevation is. A normal day can have 40+ degree swings. During one season temps can range from single digits to 80s. Thanks.
Cal,
Do your Kestrels measure dew point or just humidity %? I’ve found that many people don’t understand that the humidity numbers we frequently use are relative to temperature and are not an absolute measurement. 50% humidity at 40° is a very different moisture content than 50% at 70°. Dew point is a better measurement in many ways as that number will tell you how much moisture is in the air regardless of what temperature it is. Air is capable of holding more moisture the warmer it gets.
In your previous comment your sample that was 23% RH @ 35° (dew point of 1°) is much drier than the sample that was 43% RH @ 59° (dew point of 37°) while the 59° & 105° (dew point of 50°) samples are closer in moisture content despite the larger relative humidity differences of between those two samples.
The real elephant in the room for this particular test is how well does moisture infiltrate a loaded case and does the primer and bullet create an airtight seal or not? I would assume there could be some over time but that it would be pretty slow and take weeks at a minimum to see a significant change if there was any at all. I don’t have data to support that belief but it seems logical. That leads me to believe that as long as you loaded all of your test rounds from the same container of powder and during one session then the moisture content inside of all the cases would all be very close and would stay the same regardless of what temperature changes you later subjected the cases to. I guess that might make this whole humidity discussion irrelevant at least for this particular test.
What would be an interesting test would be to load two sets of cases with powder from the same lot but not seat bullets. Then store the two sets in environmental conditions that have significantly different moisture levels for a few days before seating bullets. After seating let both sets acclimate to the same temperature before shooting. If you then get significant velocity differences between the two sets that will tell us something about the role humidity plays.
Thanks for all the interesting info on the website.
James
Hey, James. They do measure Dew Point. Here is what I could find for that measurement, which pretty closely aligns with the math you must have done. The minor difference from your calculated values likely is a result of me picking a random point in the data, which wasn’t perfectly the average temp or average humidity … but it is very close:
105° F temp, 16% humidity, 51° F dew point
59° F temp, 43% humidity, 38° F dew point
35° F temp, 23% humidity, 0° F dew point
Honestly, I didn’t realize the differences you mentioned, and how temperature, humidity and dew point relate to one another. I appreciate you sharing that.
I do think the test you’re suggesting is very similar to what Bryan Litz and the guys from Applied Ballistics published in Modern Advancements in Long Range Shooting Volume 3. I bet you’d enjoy reading the full study, but I’ll try to quickly summarize it since I’ve referred to it a few times in the comments already.
They published data based on testing for a few different brands of powder, but I’ll share the results from one of them – because its one of the powders I tested here: H4350. Basically they acclimated one jug of H4350 to 10% relative humidity, and another one to 80% relative humidity. They let it soak for 4 days in one case, and 9 days in another. Then they loaded the exact same charge weight into 6.5 Creedmoor ammo, and measured the velocity. The powder at 10% humidity produced an average velocity of 2,823 fps, and powder at 80% humidity had an average velocity of 2,628 fps. That is a difference of 195 fps!!! The 4-day soak showed a difference of 137 fps. Either way, humidity showed to have a vastly more profound effect on velocity than ambient temperature.
That’s a pretty interesting study, and they discuss some of the practical applications they are taking away from it in the book – as well as methods you can use to ensure a stable humidity for your ammo. But, it seems pretty clear that humidity plays a huge role in powder burn characteristics.
Thanks,
Cal
Was reading your article on temp sensitivity of powders. Excellent work.
I was wondering has anyone done testing on primer temp sensitivity?
It would seem to me that you aren’t just testing powder, you are also testing primers.
Thanks for any insight you could share.
I bring this up because my primary primers are the Russian primers. They seemed to give me less sensitivity to temp in the 6×47 Lapua with H4350 and Rl16. Didn’t have Russian to compare with RL26 in my 7-300WSM.
Love all your articles. They have saved me money and I appreciate that
Hey, Justin. That’s a good question! I’m not sure I’ve ever heard someone who has intentionally tested primer temperature variance. I guess I was doing that unintentionally. I was using CCI 450 primers in all of the ammo that I tested, so I would say that it seemed to not be sensitive to temperature … at least for all practical purposes. The variance of the ammo was tiny over a 100 degree swing, so whether the slight variance was from the powder or primers or some other factor, it wasn’t significant.
If anyone else has experience with primer temperature sensitivity or knows of any research that was done, please share it with us here in the comments. Honestly, I just haven’t thought about primers being temperature sensitive, but it is plausible that some could be.
Thanks,
Cal
Have you ever considered doing similar articles for other disciplines? Like F-Class what the pro’s use? I find it interesting that the top powders aren’t the same across sports necessarily. Actions and barrels also don’t seem to be. I’m sure some of that is sponsorships but maybe some of it is merit.
Hey, Kaleb. I would find that really interesting, but I don’t compete in those other disciplines. If you have connections to someone in F-Class or Benchrest would could help me survey all of the top shooters in those sports, I’d be interested in discussing it with them. I’ve been competing in PRS-style matches since 2012, and that is where my passion lies. I’ve been fortunate to know most of the people who have owned or ran the PRS over the years, and most of them have been very open to help me gather the data I publish. But, I’ve NEVER seen any other data like this published in any other shooting discipline. Not for rifles, pistols, shotguns, or anything. I feel like it reflects the openness and culture of the PRS, where one guy is happy to help the guy next to him … even if they are top 10 competitors. I don’t think other shooting disciplines have that same culture, and I’d be shocked if the top 50 people in any other discipline would even share all of the details of what they use with all the other shooters … much less the public. That is just my hunch. But, maybe I’m wrong!
If anyone reading this has a connection with anyone who could require the top 50 or top 100 shooters in the F-Class or Benchrest world to take a survey, please chime in and I’d be happy to follow up with them. It would be cool to see what gear is common and what is different. I’d find that super-interesting!
Thanks,
Cal
Hi Cal
]
Another interesting article. When I first started reading it, I thought my powder H4350 was in real trouble because you wrote “The results? Not what I expected!”
But I soon understood that both Varget & H4350 are both excellent powders.
A few months ago I purchased a Garmin Chronograph so that could connect it to my rifle and measure each shot muzzle velocity. (now Bryan Litz stated not to connect it to my rifle, so now it beside my rifle). I simply wanted to know if there was going to be any change in muzzle velocity shooting on different days in all conditions. So your article today answers my questions about temperature and H4350.
I have learned so much from all these articles. When I first started shooting long distances I was just glad to be able to hit the target. Today I am doing everything I can to hopefully shoot only V’s or X’s. So I have gone from a guy that simply wanted to hit a long distance target to thinking only about shooting 1/2 MOA. These articles and comments all have helped.
Thanks
Paul Goggan
That’s awesome, Paul! Sounds like you’ve really come a long way. It is so rewarding to advance in long-range shooting. To me it has to be one of the most compelling challenges, because there is always more to learn and you never reach perfection.
I hadn’t heard that Litz recommends not to mount the Garmin directly to your rifle. That’s interesting.
Thanks for the kind words and encouragement. I’m glad you’ve found all this content helpful.
Thanks,
Cal
Yes I watched a YouTube video done by Bryan Litz called Understanding Muzzle Velocity. In the video he talks a lot about different Chronographs and their pros and cons.
He stated the Garmin is an excellent Radar Chronograph. He stated it very accurate, but he said if you want your best result don’t attach it to your rifle. The recoil and shockwave may cause less than 100% accuracy. It’s very small, but it’s there.
If you are shooting relying on your muzzle velocity reading being true as possible then it can make a big difference as to where your bullet lands.
Example: 6.5 Creedmoor and 140 gr bullet.
He stated if you are shooting 1000 yards and your muzzle velocity is off or wrong by 23 feet per second you would have a 6 inches drop at the target. If your muzzle velocity was off by just 11 fps it would cause a 3 inch drop.
So maybe attaching your Garmin to the rifle when you want your best data is not a good idea.
Thought I pass this information on to you.
Paul Goggan
Makes sense to me! Thanks for sharing.
Hi Cal,
Thankyou very much for bringing this article and others to live. I appreciate the time, effort and expenses that you employ.
If anything, the practical takeaway from your test to yourself is that under your test conditions, your rifle hammers and the dispersion cone is constant. That it will be another variable that you can now control during a match. Only the nut behind the bolt remains…lol
Sincerely,
Maré
Hey, Mare! Glad you found this content helpful. And I agree. That rifle hammers! It’s a bittersweet moment when you can get your rifle and ammo squared away like that, because you are right … if I miss, there is no excuses! I am the reason my rifle misses. But, I like knowing my equipment is capable and I’m the weakest link in the chain.
Thanks,
Cal
This article has been informative.
As far as data for VV, Erik Cortina keeps racking up wins in F Class with Viht and has me thinking of trying it in my 6×47 Lapua. He may have some helpful data or insight with all the rounds he has sent down range using VV.
Hi Cal,
This was an excellent article, as always! I know you are probably tired of temperature testing powders already, but I would be very interested to see how single base powders from Vihtavuori stack up to Hodgdon Extreme powders. Would you be willing to do a part 2 at some point with the same cartridges and use Vihtavuori N140 and N160?
Hey, Airwolf. Thanks for the suggestion, but I’m done temperature testing for the moment.
Thanks,
Cal
If your ammo is held in a temperature controlled container, does it matter if the powder is relative temp stable or not stable?
Hey, Marc. If you are controlling the ambient temperature of the ammo, then I can’t think of a reason temp could impact the burn rate of the powder. As others have mentioned, you might want to control humidity, too. If you’ve got a temp controlled container it seems simple enough to do both.
Thanks,
Cal