What caliber (not cartridge) is best for short barreled rifles when shooting heavy bullets?

[deerhunter628]

Now it sounds like it could be the 7mm Backcountry.

 

[The Guide]

Now it sounds like it could be the 7mm Backcountry.

If that technology correlates to other cartridges in standard actions, it really could be a game changer. If we look at the 30-06 with a 18" barrel losing 200 fps from a 24" barrel and still being a 550 yard rifle at sea level but but the new case design gives an additional 200 fps then your a 675 yard gun at sea level. Take that to 5k feet and you go from being a 650 yard rifle to an 800 yard rifle. If this technology translates to other cartridges it will make short barrels common and suppressor use easy.

Jay

 

[TheGDog]

Well, I've seen a couple vids on the new 7mm Backcountry, and the whole idea behind it is they use that newer ?HSV? steel-cases to get higher chamber pressures of like 80,000K psi rather than the typical 65,000 for a big game cartridge.

The intention is to cater to those who like hunting with suppressor and want a shorter barrel length, but don't want to have to give up soo much velocity to get it. And I wanna say with like 18" I think it was? It got like 29##fps.

And obviously they have lots of projectiles to choose from for that one since the 7mm Rem Mag has been around a while.

 

[DagOtto]

I think you would also have to define "heavy" and work from there. For me, heavy is above the following for each caliber. These are not scaled properly but just what I consider "heavy" for caliber and easily found as conventional lead core bullets. All will be the ELD line except the .277, .284, and .308 since the ELD is lighter or way heavier and I'll use the ABLR bullet for that.

224 above 73 grains
243 above 103 grains
264 above 143 grains
277 above 150 grains
284 above 168 grains
308 above 190 grains
338 above 250 grains

We should also define terminal performance limits or minimum distance for consistent upset. I will choose a distance we should all strive to be proficiency at and all rifles should have capability to of 440 yards or 1/4 of a mile. This is 402 meters for our metric friends.

Given these limitations or definitions, we can begin to calculate what velocity we would need to see to maintain or obtain complete upset with bullets of the above weights at sea level.

For the .224 caliber, you would need about 2750 fps MV to hit 1800 fps at 440 yards.

For the .243 caliber, you would need about 2520 fps MV to hit 1800 fps at 440 yards.

For the .264 caliber, you would need about 2375 fps MV to hit 1800 fps at 440 yards.

For the .277 caliber, you would need about 2375 fps MV to hit 1800 fps at 440 yards.

For the .284 caliber, you would need about 2350 fps MV to hit 1800 fps at 440 yards.

For the .308 caliber, you would need about 2365 fps MV to hit 1800 fps at 440 yards.

For the .338 caliber, you would need about 2335 fps MV to hit 1800 fps at 440 yards.

It seems that 440 yards from a 16" gun would be very obtainable with many cartridges in most calibers at sea level. As your elevation goes up the velocity at 440 yards will only increase and be better to a greater distance.

Jay

Thanks for the challenging thought exercise.

BC will make a difference on the required muzzle velocity to attain your goal impact velocity at your max defined distance.

But in general what Ive found when running these same kinds of exercises is your desired recoil level will be a major decision factor in determining the diameter bullet that is ideal.

With these more “realisitic” max shooting distances and low required MV you are going to have some fun potential cartridges to choose from in whichever diameter bullet you decide on. Except for perhaps .277 where I dont know of a pumpkin thrower cartridge. Doesnt pretty much every .277 cartridge throw pretty hot stuff?

Ive been running similar analysis for 2200 impact velocity at 400 yards. My goal being to know that any mono metal bullet will stand a great chance of fully opening / shedding petals at that max distance. In running that exercise and looking at recoils I initially was attracted to the hotter 6.8 and 7mms
Because I too run shorter suppressed barrels.

I eventually backed off of the really heavy/ high BC bullets in both diameters because I found that if you drop down one weight of bullet you can very significantly lower recoil and still meet velocity targets at 400–500 yards. For example, in 7mm this simple bullet switch allows me to drop from 7 Rem Mag to 7A.I and in the .277 diameter it allows me to drop from 6.8 Western to 6.8 WSM.

I think the point Im coming to is that it comes down to the specific bullet you choose on. And then plugging those at each diameter into a spreadsheet and then looking at reloading manuals to see which calibers will deliver the desired MV for each of the bullets at somewhere between the 3/4 and max load values in the books. From that you can narrow down ideal cartridges in each caliber and calculate recoil and make some final shortlist choices.

Fun stuff