PrecisionRifleBlog.com A DATA-DRIVEN Approach to Precision Rifles, Optics & Gear
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As long-range shooters, we tend to obsess over every little detail. After all, we’re trying to hit relatively small targets that are so far you may not even be able to see with the naked eye. While you might can get away with minor mistakes and still ring steel at short and medium ranges, as you extend the range those small mistakes or tiny inconsistencies are magnified. So, most things are important … but to differing degrees. This series of posts is taking a data-driven approach by using Applied Ballistic’s Weapon Employment Zone (WEZ) analysis tool to gain insight into how different field variables in real-world shooting affect the probability of hitting long-range targets.
I’ve played around with the WEZ tool a lot, and it was very enlightening! It challenged a lot of my long-held assumptions about how important different aspects were. As Bryan Litz said in his Accuracy & Precision for Long-Range Shooting book, “Looking at each variable separately teaches us how to assess the uncertainties of any shot and determine how critical each variable is to hitting the target.”
Previous posts looked at what impact we could expect from tightening our groups, and what we could expect from lowering our muzzle velocity SD. In this post we’ll look at another element that we handloaders tend to fixate on:
How Much Does Cartridge Matter?
Honestly, I’d be embarrassed if you knew how much time I’ve spent agonizing over cartridge selection. We love to get the absolutely highest performing bullet in the ideal case, even if that means we might have to fire-form brass and handload it ourselves. So I wanted to see how much of a difference that has on hit percentage at long-range. This is highly dependent on the loads you’re comparing, but we’ll compare a couple of the most popular rounds: the 6.5 Creedmoor and the 6mm Creedmoor. I’m also going to throw in the 308 with 175gr SMK bullets. The 308 isn’t as popular as it once was in long-range shooting, and a lot of new shooters might not understand why. This should help illustrate a big part of that. And I’m going to throw in one of the newest cartridges, a hot-rod 6.5mm cartridge known as the 26 Nosler.
Note that the external ballistics for the 6.5 Creedmoor are very similar to the 260 Rem and 6.5×47 Lapua, so you can replace 6.5 Creedmoor with one of those names if you would like. Likewise, the 6mm Creedmoor provides external ballistics very similar to the 6XC, 6×47 Lapua, and 243 Win … so you can easily replace 6mm Creedmoor with one of those cartridge names as well.
6.5 Creedmoor
- Bullet: Berger 140gr Hybrid with a Litz G7 BC of 0.320 (one of the best 6.5mm bullets available)
- Muzzle Velocity: 2850 fps (the upper end of what top PRS shooters using the 6.5mm Creedmoor reported, although many don’t run it this hot)
6mm Creedmoor
- Bullet: Berger 105gr Hybrid with a Litz G7 BC 0.278 (outstanding bullet, very high BC relative to its weight … read more on why everyone uses this bullet)
- Muzzle Velocity: 3100 fps (the upper end of what top PRS shooters using the 6mm Creedmoor reported, although many don’t run it this hot)
308 Win
- Bullet: Sierra 175gr SMK with a Litz G7 BC 0.243 (a popular bullet choice when stretching the 308 into this 700-1000 yard range)
- Muzzle Velocity: 2600 fps (advertised muzzle velocity for the popular Federal Premium ammo with this bullet)
26 Nosler
- Bullet: Berger 140gr Hybrid with a Litz G7 BC of 0.320 (one of the best 6.5mm bullets available)
- Muzzle Velocity: 3300 fps (Nosler’s reloading data for this cartridge indicates this cartridge has the potential to run this fast … that’s 15% faster than a hot 6.5 Creedmoor load running that same bullet)
For all the loads, we’ll assume we were able to achieve an great muzzle velocity standard deviation of 10 fps (see the previous post for more info on what that means). We’ll also run all of the simulations at a 0.25 MOA extreme spread, and good wind-calling ability, which means we’re able to call the wind speed within 1.25 mph 68% of the time, and within 2.5 mph 95% of the time.
Here is how it shakes out:
The first thing that pops out is the huge difference between the 308 and the other cartridges. While this isn’t a surprise to veteran shooters, it may be to some of the new guys. This is one of the big reasons there aren’t a lot of shooters running a 308 at a competitive level. The only real exception is those classes of competition that explicitly require shooters to use a 308 cartridge.
But, then we have more of a head-to-head comparison of the 6.5mm Creedmoor cartridge with the best bullet available and the 6mm Creedmoor with the best bullet available. You can see there is just a 1% difference between the 6.5 Creedmoor and 6mm Creedmoor at these ranges. That means if you fired 100 rounds, you might hit one more time with one cartridge … they’re the same for all practical purposes. Both are an massive improvement over the 308 (with significantly less recoil as well), and represent best-of-class ballistics for medium size long-range cartridges. The difference is the 6mm Creedmoor gives you those ballistics for much less recoil, but at the cost of slightly less barrel life.
And finally, the hot-rod 26 Nosler launching a 140gr bullet like a laser beam at 3,300 fps!!! To get that requires almost 90 grains of powder. While the accurate barrel life of that cartridge may be less than 1,000 rounds … it represents best of class ballistics. I ran a few other cartridges, and found a 7mm magnum (like the 7mm Rem Mag or 7mm WSM) launching a 168gr bullet at 3,000 fps produced almost identical results when you used the new Nosler Accubond Long-Range 168gr bullet with a G7 BC of .353 (G1 = .652). If that advertised BC is correct, that’s even higher than Berger’s 180gr Hybrid … but in a 168gr bullet. The 7mm Magnum option may provide slightly more barrel life, but not a lot more. Those are just smoking ballistics, and the cost to get there is less barrel life and more recoil. Even a 338 Lapua doesn’t produce a better hit percentage at those distances.
One last point to keep in mind, is that all of this analysis assumes you have centered groups. That means they represent the best case scenario for hit percentage, since your odds only decrease if groups come off center. If you’re scope isn’t zeroed, or your rifle is canted slightly to one side, or your scope’s clicks aren’t calibrated correctly, or you pull the shot slightly … then your hit probability can decrease dramatically. But these simulations assume we have all that stuff squared away.
Other Posts In This Series
This post was one of a series of posts that takes a data-driven look at what impact different elements have on getting hits at long-range. Here are some others posts in this series:
- How Much Does Group Size Matter?
- How Much Does SD Matter?
- How Much Does Cartridge Matter?
- How Much Does Muzzle Velocity Matter?
- How Much Does Accurate Ranging Matter?
- How Much Does Wind Reading Matter?
- Overall Summary
If you want to dig more into this subject or explore some of these elements for your specific rifle, ammo, and ballistics, I’d encourage you to buy the Applied Ballistics Analytics Package to run these kinds of analysis yourself. You could also pick up Bryan’s Accuracy and Precision for Long-Range Shooting book, which has a ton of great info on these topics and other aspects of shooting.
Thanks for putting this out there but if you can, please also run WEZ with accuracy of 0.4 MOA in both cases. 0.25 MOA is exceptional performance. People like me stop chasing accuracy ghost as soon as we hit 0.4-0.5 MOA. It’ll be interesting to see how much it matters in our case.
Hey, AV. It seemed like most people wanted me to run it the other way. I’m with you though. I think the way I updated this post, along with the How Much Does Group Size Matter? post should give you an idea of what you’re looking for.
Thanks,
Cal
Wish you would have run the simulation with equal SD and group size inputs…….compaire the BC and velocity strait up…..need to use more similar bullets as well if your desire is to differentiate cartridges. I’d like to see a section on how velocity affects hit percentage. Take a 6.5 mm Berger 140 hybrid and shoot it at 2850 and 3200 fps respectively with exactly the same input variables!
CJW, thanks for the input. Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
But … is there a specific cartridge you have in mind that can send a 140gr bullet at 3200 fps? I haven’t heard of many guys running that fast. I’m sure some cartridge can do it, but I just don’t know how popular something like that is or applicable to my readers. But please enlighten me.
Thanks,
Cal
Cal I like the revised version….not much reason to switch to s 6mm other than to burn up your barrel faster……I’m pushing the 140 hybrid to 3200 from a 6.5-06. It’s too much for PRS matches but I intend to use it for field style matches. Im curious how much my hit percentage improves on an MOA sized target at 500 & 1000 yds in a 10mph wind with equal sd’s and identical bullets.
CJW, I did you one better … I added ballistics for the new 26 Nosler, which according to their reloading data should be able to push a 140gr bullet up to 3300 fps. So you can now see how that compares in the diagrams in the post. That is the best ballistics I could possibly find. Not even a 338 Lapua could top it. It’s wicked fast … but I bet the barrel life is close to 800 rounds. I have a buddy with a 6.5x280AI that sent bullets 3260 and he set his barrel back at 950 rounds. His groups had opened up from 0.4-0.5 to closer to 0.75 MOA by that point. So you better not take too long on load development or have a deep wallet! But it looks awesome on paper.
Just wanted to let you know I updated the post.
Thanks,
Cal
I like it! Of all the variables it appears Velocity has the largest % increase which validates what weve always known but its cool to see the hit probability increase. Thanks for re running this analysis it makes it very clear!! I look at barrels like beer bottles, lots of work goes into making the glass to only hold 16 ounces that I can drink in less than 15 minutes. If I can get three good field matches out of a tube I’m happy, 5-7 hours on my lathe and a $320 barrel and I’ve got a 10% improvement in long range hit probability!! I love my creedmoor for run and gun stuff but out here in NM the wind blows and ranges get long and I want all the competitive advantage I can get, hence the 6.5-06 but it will only come out for serious competetions?
I’m jealous of the lathe! If I had one, I’d probably have a similar outlook.
Thanks,
Cal
Pushing a Berger 140 at 3200 is most likely just an effective way to torch a barrel as pushing a 105 at 3100, so I doubt that there is any barrel advantage. In fact, that is above even 6.5/284 territory, and those barrels seldom last 1200 rounds, and most are lost to competiton use sooner than that. Plus there is that old nemesis, recoil, and a 140 at 3200 makes A LOT more recoil than the 105 at 3100. In 15 pound guns it is almost double, 10.12 ft/lbs to 5.4. Thats almost the same recoil as a 7 WSM shooting 180’s in a 16 pound rifle. The US F Open team got beat at worlds a while back by the Brits shooting 7 WSM variants, while the US was running 6.5/284’s, so that argument is pretty much settled. I realize it might not all have been caliber related, but……
I’m past 1200 rounds with my 6XC pushing 105gr hybrids just over 3000 fps. I expect the barrel to last at least to 2000 rounds. I’m pushing just under 40gr of H4350 to get there (24″ barrel). QuickLoad says you’d need almost 50gr of H4350 to get a 140gr 6.5 bullet to 3200 fps! So no, they aren’t the same. That’s a 25% increase in powder charge. You’d likely have to go to magnum or long action cartridge (like the 6.5-06) to fit that much powder. And it would be a barrel burner. I have a good friend that chambered a 6.5x280AI, and that shot a 140gr 6.5 bullet at 3200 … Barrel lasted almost 1000 rounds. Don’t see him shooting it much anymore! The idea of a barrel burner is compelling, but most guys don’t shoot them for more than one barrel … At least not as their primary rifle. I probably shoot between 2000-3000 rounds per year out of my primary rifle, so I target cartridges with that much barrel life.
There are some outstanding 7mm billets out there. I just got some the Accubond LR bullets in, and can’t wait to work up a load for them. The 7mm bullets I have are 168gr with a G7 BC of .353!!! That’s a G1 of .652. Run the ballistics on that bullet traveling at 3000 fps. 6.4 mil drop at 1000 yards, and 13.0 mils at 1500 yards. 10mph wind drift is just 1.2 mils at 1000 yards! Hard to beat without jumping up to one of the big cartridges that hold 90gr of powder (and pack a ton more recoil).
I appreciate the comments. Thanks!
Cal
It would be interesting to see what the 6mm results would be if you assumed the 6mm were a factory cartridge (using the Berger hybrids or a Hornady 6mm bullet) with similar input data from the 6.5 (es and precision). Or the converse with hand loaded 6.5’s.
Great idea, Bob! Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
Thanks,
Cal
Cal, I enjoy most of your work. Thx. I was surprised with this article. Lower SD and better precision of course was going to win with this approach. Need to really find a better way to compare the cartridges. Dan
Dan, your wish is my command! Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
Thanks,
Cal
Thank you.
This is an awesome series of posts and certainly challenges what many of us precision?LR shooters accepted as truisms.
Honestly, it’s challenged stuff I’ve held as truisms! I’m sure there are a lot of things like that in the long-range world. We’re lucky to have people like Bryan Litz and the smart guys at Applied Ballistics who help us sort through this stuff!
Thanks,
Cal
I think it is safe to say that most hand loads (if loaded for precision) will out perform most factory loads. If you compared similar hand loads, like 6/6.5 Creemoor both using top of the line components and Berger Hybrids, what would it look like then? Would they be very close to each other? I believe so, with the only difference being the slight edge in BC to the 105 hybrids.
Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
Thanks,
Cal
Another great article. I would like to have seen the comparison using 6mm with the same accuracy potential as 6.5 factory ammo, and 6.5 handloaded ammo with the same accuracy potential as 6mm hand-loaded ammo, in other words all four scenarios. While it is good to know that there is a statistical difference in factory match and well loaded handloads, the question is how much of an advantage does 6mm have over 6.5 if all other factors are equal?
Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
Thanks,
Cal
Is this truly a comparison of SD? A muzzle velocity difference of 300fps is significant. What would the result be with the same rifle, same caliber, different SD? I like this series of articles and I appreciate your time and effort. However, this does not seem like a fair comparison.
Thanks,
Steve
Seems like a lot of people had that same idea, so I’ve updated the post based on the feedback. It now compares cartridges in a more head-to-head way, using the same SD and MOA for each one. I appreciate the feedback … it helps me make the content for useful for everyone.
Thanks,
Cal
I wish you could’ve compared the ballistics between using handloaded 140 gr Berger hybrid ammo with the same standard deviation as the handloaded 105 grain Berger hybrid hand loaded ammunition instead of comparing factory loaded ammunition against hand loaded and tuned ammo. I’m sure your data is probably sound, but is this a fair comparison to begin with?
You’re right. That would have been more valuable. I updated the post to be more of an even comparison of cartridges, with the same SD and MOA on each cartridge.
Thanks,
Cal
Wow! That’s impressive and much closer to what I would have guessed. The 6.5 has an advantage of BC, but the disadvantage of velocity. Thank you so much for such a rapid response. Now I have to dig out a recoil calculator and see which has the advantage!
The 6mm has a significant advantage. Almost 2 pounds less recoil energy, 7.69 to 5.88 foot pounds. The 6mm is actually closer to a Grendel shooting a 123 at 2650 FPS than it is to the 6.5 Creedmoor. Less recoil generally equates to less fatigue, which equates to less accuracy loss as the day goes on. Hmmm………..
The 6mm definitely has an advantage in terms of recoil. I can attest to that. I’ve shot both A LOT. Free recoil energy for the 6.5 CM is 6.79 ft/lbs, and the 6mm CM is 4.98 ft/lbs. So the 6mm provides a 27% reduction in recoil compared to the 6.5 load. See why so many are switching to a 6mm?! 😉
Thanks,
Cal
Its easy to see, but in talking to some long range guys that regularly shoot beyond 1000, they still feel like the heavier Berger 6.5 does better. I was all ready to work up a 6 Creedmoor, when they started talking to me….I’m watching and reading your posts avidly! Of course when it comes right down to it, my 7mm WSM does better than either beyond 1000, so it makes sense to go 6 CM for out to 1000, then WSM beyond until I get to .338 Lapua ranges.
That’s similar to my setup. I have a 6XC, and then a 7mm Rem Mag for 1000-1600 (have shot it out to 1 mile, but that’s stretching it into subsonic range). The external ballistics are very similar to the 6mm Creedmore and 7 WSM, but I feel like the brass selection is better. Norma brass is pretty outstanding in my experience. I’ve been debating on 6.5 Creedmoor or 338 Lapua next. Sure like the idea of shooting factory ammo for $1.20/rd, if only for practice then use the 6XC in comps. We’ll see!
Thanks,
Cal
I’ve run the 168’s at about 3100 out of my WSM, using 4831SC with no pressure signs, but the more I looked at that versus the 180’s at 2950 or so, the more I liked the 180’s. The 180 Hybrids are just so easy to get a good load with that I’ve gotten spoiled. The 168’s shot well, but I could never get them quite as tight as the 180’s, so maybe its my barrel. And my experience is that with bottlenecked cartridges the magic number seems to be 3000 FPS so far as barrel life is concerned. Stay under it and you get 30-40% more barrel life, go over and it drops precipitously. BUT, if the 168 came in a Hybrid, I might be persuaded differently. Up until now my low recoil 6.5 has been a 28″ barreled Grendel, but I readily recognize that 30 grains of powder is not enough to really play at the 700-1200 yard range, thus I’m considering on of the fast 6’s.
Cal, I like the caveat you now put in as it relates to rifle zero, cant, scope’s clicks calibration, and trigger pull. I think the only big one you now missed is correct ranging. Keep up the good work.
Oh, there is more than that! If you want a full list, you’d have to include getting a bunch of stuff right: range, temperature, altitude, humidity, latitude, incline, heading, BC, muzzle velocity, twist rate, bullet length, sight height, etc. There are a ton of variables (all with the potential to introduce error), but I was trying to keep it simple and to the point.
I did include range certainty of +/-1 yard 95% of the time (meaning the SD is 1/2 that) for these calculations. The best rangefinders produce that. I entered 0 uncertainty for those other variables I mentioned, just to keep it simpler (and keep people from arguing too much!).
Thanks,
Cal
One of the biggest problems with these theoretical loads is making sure that they are realistic in the end of the day. To take it to the next level, you need a combination of OBT calculator, Quickload and AB Analytics. This then allows you to compare the ‘possible’ speed at a specific load and barrel length to hit an accuracy ‘node’… then you can look at the resulting fps.
Although at Long Range this might not actually apply as much, as inherent rifle accuracy (rifle’s MOA) has less of an effect on Hit Percentage, as changing the MOA (extreme spread) from 0.25 to 1 MOA has only around a 2% effect on hit rate.
So; forget the quality of the rifle to a degree, and focus on:
– Getting a great BC to weight ratio bullet, and run it as fast as possible at just over a 1.5 SG
– Getting really good at estimating wind (close wind matters more)
– Producing the most consistent ammo
– Get the best range finder that money can buy
Hmmm… I think there is another article in there. (I’d better get writing)
Yep, lots of good points. Most of those I’ve hit on in this series. I’d love to read what you come up, so when it’s published please come back and give us a link.
Thanks,
Cal
Cal great article! It’s amazing the amount of work you put in to all of your articles and the amount of people it has helped including myself.
Searching through your blogs the one interesting thing I would be interested to know is what the top shooters in the precision rifle series use for barrel length in each caliber…. Both 6.5 and 6mm from what I read all over seems that 26 inches is what everyone uses but would be curious to see what the top guys do. Any idea by chance since you interact with these guys?
Again great great work and than your for helping me by providing a wealth of information to break into precision long range.
Hey, DC. Glad your finding the content helpful. I actually posted data on that specific thing. I listed the what barrels lengths the top 50 shooters in the PRS are using, and even broke it down by cartridge. You can check that out in this post:
Rifle Barrels – What The Pros Use
Thanks,
Cal
Only thing I would suggest is to change the 26 nosler down to 3180fps. The reasoning is that you mentioned PRS shooters a couple of times so lets keep it to PRS rules. In 2015 there is a strict 3200fps speed limit, in 2014 it was 3150fps +/- 10% or 30fps. So lets drop the 26 nosler down to 3180fps which is about the fastest anyone will run any cartridge in the PRS and see what that does. I think posting those numbers will show all of the guys interested in building a 6.5 SAUM what the actual difference is taking the 140 hybrid from 2850fps to 3150fps.
love your reading your articles, always something interesting to read. and like a few already mentioned and you already fixed, when comparing certain things minimizing variables is the best way. same accuracy and SD across the board shows the deviation of what we are actually comparing!
keep up the good work!
Hey, Matt. Your right, most competitions limit people to 3200 fps. They just don’t want people to damage their steel targets, and I can understand that.
In this post, I was just trying to illustrate the upper end of cartridges, or how far you could take it. If you wanted the same ballistic advantage, you could get it and still stay under the 3200 fps rules. You could run a 7mm magnum like the 7mm Ultra Mag pushing a Nosler 168gr Accubond LR at 3150 fps, and you’d have very similar ballistics to what is shown for the 26 Nosler. They both have 1″ of drop at 1,000 yards (joking). Both are ridiculous cartridges that come with very short barrel life standard, but if you really want to squeeze out every last drop of ballistic advantage … those are pretty good options.
I don’t see a lot of guys going to either cartridge for PRS type competitions. I was just trying to make an illustration as to how far you could push it. At the last competition I was at, I saw one of the top competitors running a 7mm SAUM, but that stood out as unusual (although it’s a great cartridge). Most guys use mid-size 6mm and 6.5mm cartridges. Some guys go with hotrods for their first precision rifle build, but when they rebarrel they typically go with a more moderate cartridge. Barrel life is something that you can easily underestimate the value of … until you don’t have any. Changing barrels mid-season is not a great option. I prefer my barrels to last a full year, and I know a lot of the other guys try to find a similar balance as well. We like to get as close as we can to the line, but I doubt anyone in the top 50 will be running a 26 Nosler next year. It’s just too much work to change out the barrel when you shoot as many rounds as what those guys do. I’ve probably shot 2000 rounds this year already. If your accurate barrel life is 800 rounds (which I bet is what the 26 Nosler provides), that would be an expensive (and/or inconvenient) proposition.
Thanks for the feedback. Glad you’re enjoying the content.
Cal
This is the type of posts we need to see more of.
Thanks
I loved the article. Only one thing I would like to see different. You used the absolute best b.c. projectile in every cartridge and absolute screaming velocities in every cartridge EXCEPT the 308. A 175 SMK at 2,600 is pretty sad. Try a Berger 185 hybrid at 2,700-2,750 fps.
The 175gr SMK at 2600 fps is representative of what the Federal Premium ammo runs in many 308’s. That is what a lot of 308 shooters are using, if they are trying to stretch it out to these distances. And I looked at the Berger Reloading Manual, and the fastest muzzle velocity for the max load on the 185gr bullets in 308 is 2620 fps. So it sounds like your muzzle velocities might either be optimistic or exceeding the recommended pressures.
I changed laptops and don’t have the AB software loaded on this one yet, so I can’t run the other numbers. My bet is it doesn’t change it as much as you think it would. The 308 is just ballistically handicapped when it comes to these other rounds, especially when you consider recoil.
Hey, I’m not tell you to change cartridges. If you like your 308 … keep shooting it. Don’t fix happy. But this is a very objective comparison that shows the shortcomings of that cartridge in terms of external ballistics. If you don’t need the energy downrange and you aren’t shooting in a competition that explicitly requires the 308, then there are likely better options out there if you’re looking to maximize your hits at long-range.
Thanks,
Cal
I think you’re absolutely correct that the .308 is at a disadvantage, but to say it’s an objective test is kind’ve pushing it. You say yourself they’re hot handloads for the 6 and the 6.5, but the 308 is just standard stuff. Since the load data is geared towards competition shooting, I checked the 2015 f-class nationals (“a lot of 308 shooters…trying to stretch it out to these distances”), and not a single one was using 175 SMK. All used 185 gr up to 215gr., almost exclusively Bergers. Yes, I know F-class and PRS are totally different.
Again, I want to stress, I absolutely loved the article. I’m not trying to disparage you at all. Just making some friendly observations. I wish I could afford the software, I would play with it all day!
I appreciate the feedback, and wish I had the software to run the simulation on this machine. I’d be shocked if it made that big of a difference at all. Even at the optimistic muzzle velocities that you stated, you might be able to break into 60% … but I’d be shocked if it could get to 65%. I don’t know that, but that is just my guess after running lots of different simulations. It just doesn’t make as big of a difference as you would think. If you really want to know, buy the software and check for yourself. If you’re happy with the heavy bullets in the 308, that is great. Don’t fix happy. But, I’m done arguing about it at this point.
Thanks,
Cal
Cal,
I got here a bit late, sorry. I am sure the central premise of the analysis is correct 6.5 XX will be more ballistically efficient than 308 but you do yourself a disservice with the selection of the old 175gr load. There are too many articles which try to present the new hotshot cartridge by comparing its extreme, hand loaded performance against a 30 year old factory load as the comparison. Not your intention, I know but it is interesting to 308 guys to understand the real differences on a comparable basis.
I ran an analysis on a 308 with a 185 gr Hybrid based on a load Lowlight had for the Juggxrnaught in a 22″ barrel, so it is real and it is not extreme. I have achieve those speeds with different powders and bullets of that weight in my rifle so more than one data point. I was careful to replicate your results on the 6.5’s then applied those parameters to that load.
So on the 10″ target at 700 yards the hit percentage was 70% and on the 1000 yard 20″ target this dropped to 64%. That paints a bit of a different picture without changing the central thesis – the 6.5 is a ballistically more efficient choice.
However rather than a 6.5CM seeing a 24%-30% improvement over the 308, this analysis suggests is more likely to be in the region of 10%-11%. (I ignored the 26N as that speed isn’t legal in PRS and it is a different class cartridge anyway.)
Not so dramatic a difference when you compare loadings with modern bullets and powders.
So if you are a 308 shooter that analysis says change the barrel if you want to be competitive and change your reloading if you don’t want to change the barrel.
In summary, a 6.5CM loading could give a 10% improvement in Hit Percentages over a modern 308W load compared with a 30% improvement over a ‘traditional’ load.
Hey, Andy. I appreciate your input. The 175gr SMK seems to be the most opular bullet shot for those trying to shoot long range with a 308, but I re-ran the calculations for the 308 using the 185gr Hybrid at 2600 fps. I’m not sure what muzzle velocity you were running those at, but 2600 fps is the fastest velocity listed in the Berger Reloading Manual for a 24″ barrel. So anything more than that may be pushing the boundary of safety.
But, the 185gr Hybrid at 2600 fps (and the identical set of other variance/uncertainties that the analysis above was ran at for muzzle velocity, dispersion, wind, range, etc.) produces a hit probability of 65% on the 10″ target at 700 yards. So that is still 14% lower than any of the other cartridges listed here. On the 20″ target at 1000 yards it provides a 58% hit probability, which is at least 16% lower than the other cartridges.
The 185gr Hybrid does certainly maximize the long-range performance of the 308 … but it is still significantly out-performed by these other cartridges. On average, these other cartridges would give you 15% more hits, which is a big deal. I’m not saying to sell your 308. Just know that you could be hitting more targets with a different cartridge. It’s just the truth of it.
Thanks,
Cal
Interesting post. What happens if you use a high BC bullet in the .308 such as the 190gr Nosler accubond LR? (.640 G1 bc) Would the hit probability increase versus the 175 SMK even if the load was only going 2575 (Lyman manual)
Are there other combinations in the .308 that may significantly raise the hit probability? I understand that it can’t compete with the best, but surely it can do better?
There might be a combination that slightly increases hit probability, but it’s unlikely that any would “significantly raise the hit probability” without exceeding recommended loads. I don’t have the software loaded on my new laptop yet, but I’d suggest that you purchase it and play around with it. You can learn an awful lot with that software, and the ad hoc analysis of just trying different loads and getting quick feedback is the most powerful part of it.
Thanks,
Cal