Reloading standard cartridges in short barrels

[YZ-80]

Hi all,
Looks like I'm gonna get a 20" .308 and I've never reloaded for the "shorties". I'm used to reloading for 24-26" barrels with better than average results. What will change with the shorter barrel? Say my standard load in a 1:10" 24" 308 is 42 grains of Varget under a 168 ELD-M. All things being equal, can I expect that load to perform just as well out of a 20" bbl? Is it likely that I'll have to switch to a faster burning powder?

I've also read that some of these short barreled .308's like the heavies (175-178 grainers) which seems counterintuitive to me. Wouldn't a shorter tube have a harder time stabilizing a heavier bullet at a givin twist rate?

 

[David Emerson]

I forget in who,s book or when but the article I read whatever powder gives the best speed in a long barrel will give the best speed in short too. And the short barrel should be more accurate as it is stiffer. As far as stabilizing twist is twist short or long. As far as liking the heavies maybe less velocity loss with a heavier bullet? I am not sure. Only factor in twist would be if the barrel was so short and not enough speed to get enough rpm. Then you would need a faster twist.

 

[sturner]

I'm shooting 168 AMax in a 1/10 twist
2456 fps
42.5 Varget
What fps you getting out of your longer barrel?

 

[PApa Black]

308, Savage 116, 22" barrel w/ StraightJacket, 1:10T. Elevation 10ft ( South Louisiana)
Berger 168 VLD

Federal 210M

IMR 8208 XBR

42.4

2.100" +/- .001" CBTO

2.790" +/- .002 COAL

2763 FPS @ 72°F, 99% Hum

100 yd = 0.428" (5) Shot

 

[aushunter1]

Personally for shorter 20' barrels I recon you should go with a powder on the slightly faster end of the burn rate scale, still suitable to the projectile weight if course.
If your using the slower end of the plectrum you may not get 100% powder burn & lose even more velocity.

Just my theory anyway.

 

[YZ-80]

I'm shooting 168 AMax in a 1/10 twist
2456 fps
42.5 Varget
What fps you getting out of your longer barrel?

I'm getting 2,700 FPS on the magnetospeed from that 42 grain charge.

 

[Wilderness Blacktail]

I forget in who,s book or when but the article I read whatever powder gives the best speed in a long barrel will give the best speed in short too. And the short barrel should be more accurate as it is stiffer. As far as stabilizing twist is twist short or long. As far as liking the heavies maybe less velocity loss with a heavier bullet? I am not sure. Only factor in twist would be if the barrel was so short and not enough speed to get enough rpm. Then you would need a faster twist.

Was it John Barsness? I know he has done some work with this and has said that the same powders that gave the top speeds in long barrel were gunna do the same in the shorter barrel.

 

[Steves1911]

I have a 20" 308 with a 11twist. Shoots the 168eldm over 44gr rl15 @2690fps. It does well with varget and imr4064 too. Stabilizes 180gr nosler ballistic tips and hornady 178hr bthp fine. 308 works well in a 20" tube and makes for a very handy package.

 

[sturner]

I'm getting 2,700 FPS on the magnetospeed from that 42 grain charge.

Shot my through my Ohler
With .5 more Varget 244 FPS slower and 4"less barrel

 

[cohunt]

I have a 16" 308 and tried 5 different powers in the "fast" range-- ended up going back to varget for best accuracy-- the faster powders still hit peak pressure earlier than std powders so they still tend to pressure out before std powders do. Most powder burns on the first 6-7 inches --- the reason slower powders work well in longer barrels is that they sustain the pressure longer.
As far as bullet weight is concerned, its gonna be what the barrel likes.

It's the pressure under the curve that creates speed not peak pressure.

 

[David Emerson]

Was it John Barsness? I know he has done some work with this and has said that the same powders that gave the top speeds in long barrel were gunna do the same in the shorter barrel.

It could be.Read it so long ago it has slipped the memory bank

 

[yorke-1]

I wouldn't count on the load that was most accurate in the long barrel still being the most accurate in the short barrel. You might get lucky though! I've had good luck with the same load in the 6mm BR in 26" and 30" rifles as well as an 18" specialty pistol; 30.3gr of Varget and a 105 Berger shoots well in every 6mm BR LOL. I know there are a lot of "go-to" loads that work in the 308 too.

Don't worry about going to a faster powder just because you're using a shorter barrel. I've done a lot of shooting with various long and short barrel guns in the same chamberings and the powder that gives the highest velocity in a long barrel still gives the highest velocity in a short barrel. This has held true for cases burning anywhere from 25gr of powder up through 145gr of powder. That doesn't mean that it will still be the most accurate though.

 

[bigedp51]

308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)
https://rifleshooter.com/2014/12/30...ato-barrel-length-versus-velocity-28-to-16-5/

Below a 16.5 inch barrel

Below a 24 inch barrel and higher velocities.

 

[dfanonymous]

I use the a 178 eld in a 20 inch. Factory ammo is chrono'd at 2578 @85 degrees F and verified at 1500 yards. My hand loads I use 43.2 grains of varget. However the hornady manual says max is pretty much 42 gr for varget. I was loading for this bullet before the book came out using a Lyman manual and under the amax standard. So that's how I found out that I could push the bullet into the 2500 range. Chrono'd 2535 in 65 degree F. Only verified to 1200 yards. All at 2000ft. I really don't touch it now as I've been looking at doing another powder to see how far I could launch it. Varget is probably not the powder for that. I might try 2460 later. However my stock remington just shoots. Even factory ammo group well, about .5 moa. Reducing ES is about the only thing I get benefit for reloading in the particular gun. I dropped it from about 18 in factory ammo to about 10 with varget.