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How do you find the optimal rifle powder and load? Rifle load development can often be a trial-and-error effort where you have to put a lot of rounds through your barrel to learn what it likes best. The problem is that we’re trying to detect relatively minor performance differences between loads (e.g., one load has a 0.35 MOA group, and another might be 0.45 MOA). When you’re trying to differentiate between those minor differences, you need a large sample size to know with any confidence that what you’re seeing isn’t simply random noise in the data. (Read my Statistics for Shooters Who Aren’t Math Nerds articles for more details.)
That means if we are going to try a couple of different types of reloading powders and charge weights, then we’ll quickly end up putting hundreds of rounds on our barrel before we find the optimal load. For a barrel like the 6mm Creedmoor that may only have 900-1200 rounds of accurate barrel life, using up a significant portion of that to find a load is sure hard on your wallet! 😉
This guide will show you how to streamline your reloading process and pick the best rifle powder for your cartridge.
My Old Shortcut: Try What The Pros Use
The only shortcut I knew of was to try what the top-ranked precision rifle shooters were using, and maybe that would get me on a very accurate load quickly. I published very detailed load data from top 200 shooters in the PRS, and it’s often where I personally go to get an idea of what loads to try:
- 6mm Dasher Load Data – What The Pros Use
- 6 & 6.5 Creedmoor Load Data – What The Pros Use
- 6BRA, 6BRX & 6BR Load Data – What The Pros Use
- 6×47 and 6.5×47 Lapua Load Data – What The Pros Use
- 6XC Load Data – What The Pros Use
If you’re looking for another cartridge, you can also browse my personal load data. That’s the page where I save all my load data and reference back to it when I’m reloading.
I will warn anyone thinking about copying someone else’s load data to start with the minimum safe loads from a reloading manual and slowly work your way up to the load. Never assume a load that was safe in someone else’s rifle will also be safe in your rifle too.
A Professional Ballistician’s Approach To Load Development
Then, a few weeks ago, I came across the book Ammunition, Demystified by Jeff Siewert (view book on Amazon | read my review of the book) – and I’ve learned a ton about ammo! It’s literally one of the best books I’ve ever come across related to precision rifles and long-range shooting. It is written by a ballistic engineer who recently retired after a 40-year career of research and development relating to ammo and firearms, and the book is his way of pulling back the curtain on the “black magic” of ammunition and sharing the facts and insights he learned through decades of research and being an industry insider.
Jayden Quinlan, senior ballistician at Hornady, says that he finds himself pulling this book off his shelf weekly to reference something. It is fascinating, and I don’t think anything like it has ever been published.
Here is the intro to one of the sections in the book:
“I’ve read lots of articles in various publications about the effect propellant has on the dispersion of a given load, most of it well-intentioned, but nearly all is sorely lacking in explanation as to the particular parameters leading to a particular propellant being responsible for shooting a small group size.” – Jeff Siewart in Ammunition, Demystified
Jeff systematically outlines all of the specific factors that cause powders to fire small groups or not. Jeff not only agrees that the powder you use can impact your dispersion but explains all of the intricacies of how powder can change a bullet’s flight.
I won’t spoil it all, but I did want to share a few practical tips that Jeff covers in his book.
There are three primary ways changes in propellant can adversely affect dispersion, even if you put precisely the same weight of propellant in the same case.
- If the propellant is too slow for the application at hand, the case may be filed with powder, but the propellant likely won’t completely burn out prior to the projectile exiting the barrel. The unburned propellant grains subject the base of the projectile to a hail of small, externally applied loads, oriented randomly (around the circumference of the projectile as viewed from the base), that can push the projectile around. While the loads imparted by the unburned propellant grains impacting the projectile may be small, spin-stabilized projectiles are especially sensitive to externally applied loads at their aft end. Another possibility with a propellant that is too slow for the intended application is that it usually results in higher than desired pressure on the projectile base at the muzzle exit. High but variable base pressure at muzzle exit, combined with a mechanical asymmetry at the muzzle (imperfect muzzle crown), can impart variable unbalanced loads to the projectile base, disturbing the projectile flight. …
- If the propellant is too fast for the application at hand, the case will not be completely filled with propellant (if we’re paying attention to pressure limits). With the case less than 100% full, there will frequently be a shot-to-shot variation in the distribution of the propellant in the case as the primer is initiated. Variation in propellant distribution at ignition leads to variations in flame spread through the propellant bed, leading to larger than desired variations of peak pressure, time to peak pressure, muzzle velocity, and in-bore travel time shot-to-shot. … Since there are no straight barrels, variations in peak pressure, muzzle velocity, and action time lead to changes in barrel pointing vector as the bullet exits the barrel, increasing dispersion. In this particular instance, an inert filling, such as powdered baby cereal, over the propellant bed aft of the projectile can prevent propellant from wandering around in the case during handling and chambering and potentially reduce shot-to-shot variations harmful to good dispersion.”
- … and you’ll have to read the book to see the 3rd factor. It’s on page 132.
In the book, Jeff points out several nuanced tradeoffs between different powder characteristics. By understanding the science and physics of what is actually happening, we can make better decisions in terms of what “striking the right balance” might look like for our rifle and application.
Every cartridge has a variety of appropriate powders from which we can choose, which are listed as options in reloading manuals. Which powder should we try first? A professional ballistician often has a sense as to which powders are most likely to produce the smallest groups.
Because Jeff was an industry insider for 40 years, he shares valuable insight in terms of observations that several small-caliber ammunition manufacturers have made in terms of what types of powders seem to be associated with smaller groups. It’s always interesting when you see multiple independent teams come to similar conclusions.
“One interesting observation that has been made by several small caliber ammunition suppliers is that, all else being equal (e.g., for given case/bullet combination and given muzzle velocity), smaller groups are associated with propellants having higher relative quickness. This means that the bullet attains a given peak pressure earlier in its in-bore travel and significantly has reduced base pressure as the bullet exits the barrel. Any tilt of the bullet in-bore with respect to the bore centerline will generate a flow asymmetry at muzzle exit, inducing an angular rate on the projectile. Use of powder with increased relative quickness would be expected to see a reduction in both base pressure at muzzle exit and the frequency of unburned propellant grains exiting the barrel. Both these should help reduce group size.”
When we’re doing rifle load development in search of the smallest groups and best precision, Jeff says what we’re really doing is looking for a powder that burns out completely while filling the case as close to 100% loading density as possible without exceeding the allowable pressure.
Here is how he summarizes a professional ballistician’s approach to load development in terms of what attributes they’re going to look for in a reloading powder:
As partially stated above, the ideal propellant for a particular application possesses these attributes:
- The case is filled to greater than 95%-97% of the maximum bulk loaded density to maximize muzzle velocity.
- Peak maximum operating pressure of the weapon is not exceeded on a frequent basis.
- The propellant grains are completely consumed prior to the projectile exit from the muzzle.
- The propellant is easy to ignite when conditioned at cold temperatures without becoming brittle. 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.
- The propellant has a low temperature coefficient; its performance is not overly sensitive to increases or decreases in ambient temperature.”
If you’re still reading this article, then I guarantee you’ll love Jeff’s book. There are a ton more nuggets of wisdom in there that I’d love to share, but you should just go buy it!
Coming Up Next
My next article will dive deeper into Jeff’s last bullet point above, which is rifle powder temperature sensitivity. I’ll share insight from another group of professional ballisticians who literally produce over 100 million rounds of ammo every year. I’ll also quantify what that means to the long-range shooter in practical terms. Stay tuned!
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
- Rifle Powder Temperature Sensitivity – Why It Matters & Best Powders To Use (coming soon)
- 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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“Accuracy” Really?
Ha! I actually hate it when people confuse accuracy and precision – but unfortunately, that is what most people search for when they’re looking for content like this. So, in an attempt to make this article easier for people to find when they’re searching for info like this … I took the advice of ChatGPT and used the word accuracy in the title.
Honestly, I’m just trying to help people … and if people never come across my article, then I’m not helping them.
Thanks,
Cal
This is pretty fascinating stuff. I just had a 7 PRC built by my guy and I’m now about to create some loads for it. Hopefully this book and your info will guide my efforts. Glad I got your email. Thanks
I thought it was very interesting, too. I had been thinking the slower burning the powder the better, but this seems to point in the opposite direction. How Jeff explained it all makes a lot of sense though. Of course, the book has a lot more depth into the explanation.
Glad the timing worked out great for you!
Thanks,
Cal
Interesting post! I’m just getting into reloading, and it’s interesting seeing case fill on vihtavuori powder, for instance, as it typically takes up more volume (from my understanding, at least). Would N570 work well for 300NM compared to something else just do to the amount of case volume it fills up, I wonder?
As a beginner, where can I find data to verify the following you said were important:
-“case is filled to greater than 95%-97% of the maximum bulk loaded density to maximize muzzle velocity.”
-“Peak maximum operating pressure of the weapon is not exceeded on a frequent basis.”
-The propellant grains are completely consumed prior to the projectile exit from the muzzle.
-No nitroglycerin
-Low temp coefficient
Do I just reach out to each powder manufacturer? Or is this in a specific reloading book? Thanks so much!
Hey, Michael. That is a great question. In my next article, I’ll share some insight from another group of ballistic engineers on what specific types of powders they’ve found to have the lowest temperature sensitivity. So, I feel like the next article will at least give you some good insight into that part.
As far as the other info you are looking for, the only tool I have experience with that can give you insight is QuickLoad. But it looks like there are a few on the market that might be relevant, at least according to ChatGPT. Here are the 3 it mentioned:
QuickLOAD: QuickLOAD is a comprehensive internal ballistics predictor that allows users to simulate various reloading scenarios. It provides detailed information on case fill percentages, peak pressures, and burn rates to ensure safe and efficient loads. Users can input specific cartridge and bullet data to receive tailored predictions. Pricing for QuickLOAD varies by region, but it typically ranges around $150 to $200.
Gordons Reloading Tool (GRT): GRT is a free, open-source internal ballistics simulation tool. It provides users with insights into case fill ratios, pressure curves, and combustion completeness. The software is continually updated by a community of enthusiasts and offers a wide range of features comparable to commercial options.
Load From a Disk: This software offers detailed reloading data and ballistic predictions. It helps users assess case capacities, pressures, and burn characteristics for different powder and bullet combinations. The program also includes a database of powders and projectiles to facilitate accurate simulations. The pricing for Load From a Disk is approximately $65.
I’ll say that QuickLOAD is a pretty old code base and UI, but it tends to be the software package I here other people referencing the most. It’s the only one I have personal experience with too. It’s not the most user-friendly software, but it does seem fairly comprehensive.
I’d think the powder manufacturers could also help give you personalized recommendations, if you reached out to them. I’ll also say that the Berger Reloading Manual provides “Approximate Fill Ratio” for each of the loads in the manual, which is helpful to narrow it down … without any technical calculations or software needed.
Hope this is helpful! If anyone else knows of others ways you could get insight into this, please chime in here in the comments.
Thanks,
Cal
Hey, Michael. I should have also mentioned, you said “No nitroglycerin.” I don’t think you have to take that stark of a stance. In the book, Jeff explains “Double base powders are about 80-85% nitrocellulose, along with about 8-10% nitroglycerine, increasing the energy of the powder compared to single-base propellants.” So all double-base powders have some level of nitroglycerin in them, where all single-base powders are absent of nitroglycerin. I wouldn’t just write off all double-base powders. Some of them are able to mitigate the downsides of nitroglycerin through advanced coatings and techniques. Hodgdon Varget and H4350 are great single-base powders, but there are also powders like Reloder 26 that are double-base powders that have a lot of the characteristics that shooters look for in a consistent powder. In fact, I’ll share more on that in the next article.
I don’t think Jeff was necessarily saying that a double-base powder would NEVER be the optimal powder to use. It’s just that if you’re using it well below freezing, then there are some nuances to it you should be aware of and potentially test your ammo in those conditions if you are going to potentially be shooting in them.
Thanks,
Cal
Thanks for a little more info on this book. I went to buy it but the $36.55 price wasn’t there. Is that offer expired?
It pulls the price info from Amazon dynamically. I didn’t enter it. So, I’m not sure. But I just tried it myself and saw the same thing. Kind of frustrating. Sorry!
Thanks for a little more info on this book. I went to buy it but the $36.55 price wasn’t there. Is that offer expired?
Okay, I ordered the book and made a donation. Thank You for creating the Precision Rifle Blog content.
Walmart has it for $35
I would have never guessed that Walmart would sell this book, but sure enough.
I have used Design of Experiments (DOE) for manufacturing process optimization, and to reduce variation. The enemy of quality is variation. I would love to see results of actual DOE’s from one of the ammunition statisticians on what Factors they used in their experiments, and which Factors were found to be significant vs insignificant.
Oh, man. I’d love to see that, too. I feel like the best I’ve seen towards that effort with a true emperical/scientific based approach is Bryan Litz in Modern Advancements in Long Range Shooting Vol 2. In that, he tests bullet pointing and trimming, powder measurement, flash hole deburring, neck tension, and fill ratio. You might find that interesting, if you haven’t read it already.
The problem with most real testing like that is it requires isolating one variable at a time and a TON of rounds, because we’re also trying to tell relatively small differences (e.g., 0.25 MOA vs 0.35 MOA). So to come to any conclusion that you can have a high level of confidence in (and not simply noise in the data) typically requires 50+ rounds for each permutation. I think that’s why we haven’t seen a truly comprehensive study on it. But, one day I hope to have the time to undertake such a study in my tunnel. I don’t have the time at this point, but maybe in a few years after my kids are grown I can dedicate the time. It would be VERY interesting, and I feel like the fully controlled environment of my 100 yard underground range could help me isolate some of the noise that most people would have to manage shooting outside, so maybe I could reach firm conclusions in fewer shots. I would suspect it still might require 5,000+ rounds to do the testing that I have in mind. So it’d cost a lot, but maybe one day.
If anyone knows of another study that has been done like what Mark is talking about that tries to identify what is found to significant in terms of ammo loading, please share it here in the comments!
Thanks,
Cal
There are statistical techniques used in Design of Experiments to minimize the number of Experiments. DOE do NOT use One Factor at a time (OFAT) experiments. Each DOE run changes all variables (Factors) in a systematic way. See Taguchi methods.
Well, that would be convenient! I’ll check it out.
Thanks,
Cal
Here is exactly the difference between Hunting and Target Shooting. (That’s not criticism.) If the variance (statistically speaking) is so small that it requires *hundreds” if not *thousands* of rounds to obtain a statistically significant sample, then the only people the variable *should* matter to are professional target shooters. The OTHER variables in a hunting scenario ALWAYS overwhelm variables that add statically to the overall variance between shots.
I understand. This is the “Precision Rifle Blog”. Furthermore, I appreciate the ‘attention to detail’, presented here. Nevertheless, there are ‘issues’ I have with presentations like this. One is that there is no disclaimer regarding the *practical* applicability of the information presented. (The comment regarding 0.25 MoA vs 0.35 MoA notwithstanding as that is not a disclaimer to the statistically untrained.) Second, this kind of info, presented without qualification regarding applicability, leads to conflict when the statistically ignorant try to argue that “this” or “that” matter to an “ethical” (ptooey) Hunter.
Finally, I built a 7mmx300 Weatherby in my “speed uber alles” days. I did so because some woman (sorry. I forget her name) just set the world record 10-shot, 1000yd group with a rifle chambered in that cartridge. I used 78 grains of I4831, ad shot tiny little cloverleafs ‘all day long’. One day at the range doing some chrono work, I had a 4’*8′ sheet of plywood out in front of my rifle so the chrono had good footing. When I got up to check targets, there was a *ton* of unburnt powder on the plywood. Yikes! “Obviously” I was using too much powder. I spent MONTHS changing charges, changing powders, adding a variety of fillers, without success. NOTHING I did produced the small groups that the original “best load” produced. To this day, when striving for the most precise loads. I look for powders that give “100% burn in the barrel” powders. Nevertheless, as a trained scientist and engineer, I do not let theory override observation.
Paul
Paul, I agree with your skepticism. If this content doesn’t match your experience, then toss it aside. I’d say what Jeff is presenting is what tends to produce the best results, but it stands to reason that there are always exceptions. However, Jeff referenced things that several small arms ammunition manufacturers have observed in their expensive testing. So rather than stand on your exception as the rule, I’d tend to agree with the guy who has 40 years of experience as an industry insider and professional ballistic engineer. I’m not downplaying your experience. I will say I have a great load for a 7mm Rem Mag that is based on a relatively slow burning powder for it, but I’m not going to rework that load just because of this new information. If a load already groups well, then knowing these best practices or common trends won’t make it shoot worse. So in that way, I’m with you.
I do appreciate knowing the logic and physics behind what Jeff presented. I never thought unburned granules could possibly knock a bullet off course in a meaningful way, until I heard Jeff give a thorough explanation of why. In fact, I’ve seen some diagrams he’s made that help me get a picture of it in my mind.
My comment of thousands of rounds was replying to Mark, who was saying, “I would love to see results of actual DOE’s from one of the ammunition statisticians on what Factors they used in their experiments, and which Factors were found to be significant vs insignificant.” So, Mark is not saying he would like to see what a hunter would do to determine if one load is better than another. He said “one of the ammunition statisticians,” so my reply was in context of that.
I’d also say that the overwhelming majority of reloaders draw conclusions based on a sample size that wouldn’t support their conclusion a level of confidence much above 50%. I’ve written a 3 part series where I desperately tried to explain it in a way that you don’t have to be a math nerd to understand: Statistics for Shooters. I’ve never put more effort into anything I’ve written, because I thought it was so important for the average reloader to understand. But, it’s not just me that believes that. The Hornady ballisticians have tried to explain that many, many times. Here is a podcast they did on it, which I think explains it well:
I’d say if someone is firing 5-shot groups or 10-shot groups to determine if one load is better than another, you are simply fooling yourself. They think they’re seeing a meaningful pattern in meaningless noise, and if they repeated the shots – they’d see a different pattern. If one group isn’t double the size of the other, then any minor differences are in the noise. That is not only if you are trying to differentiate between 0.25 and 0.35 MOA … but even if you are trying to differentiate between 0.5 and 0.8 MOA. There are actually statistical calculations you can do to see how likely what you are seeing is to repeat in the future, and how much confidence you can have that the difference isn’t simply noise. I explain that in those articles. I believe that isn’t simply academic or only for the elite precision shooters, but it’s useful for anyone doing load development to understand those things. Honestly, after understanding them fully myself – my load development process has changed dramatically. It turns out ammo isn’t as finicky as I once thought, which became clear to me after I changed how I went about finding the “perfect load.”
I do think what Mark was referring to is a definitive study that would rank what is most important when it comes to load development, and that research effort would require literally thousands of shots. My load development does not require thousands of shots. In fact, it requires much, much less … now that I understand the science and statistics behind it.
So I appreciate your point. Everyone is welcome to their own opinion, but I do think some of this is relevant to many hunters, too … and not just those competing or shooting groups.
Thanks,
Cal