Thread: Projectile vs barrel length

.308 Win Barrel Cut-Down Test: Velocity vs. Barrel Length « Daily Bulletin
If what you're saying was true, the above experiment would not have documented a 261fts drop in mv when they sawed off the barrel from 28" all the way down to 16". They average was a loss of 22.5fts loss per inch
So, the powder ain't burning past 3 or 4 inches but that really is semantics. The bullet is still accelerating all the way up so a shorter barrel does leak a crap load of wasted 'expanding gas' shall we call it.
Your post did make me go looking and a lot of guys find unburnt powder but that's due to the oxygen being depleted apparently and nothing to do with barrel length

Originally Posted by Dead is better

.308 Win Barrel Cut-Down Test: Velocity vs. Barrel Length « Daily Bulletin
If what you're saying was true, the above experiment would not have documented a 261fts drop in mv when they sawed off the barrel from 28" all the way down to 16". They average was a loss of 22.5fts loss per inch
So, the powder ain't burning past 3 or 4 inches but that really is semantics. The bullet is still accelerating all the way up so a shorter barrel does leak a crap load of wasted 'expanding gas' shall we call it.
Your post did make me go looking and a lot of guys find unburnt powder but that's due to the oxygen being depleted apparently and nothing to do with barrel length

Yes if you chop a barrel you loose velocity. Iv said that already. Yes you may not be burning all of the powder because of the shorter barrel and there could well be some kernels that didn't ignite and yes there will be more gas wasted as you put it, (more muzzle blast). They are all symptoms of a shorter barrel.
None of which changes the fact that you can not win back velocity by switching to a faster burn rate. .

You have QL, while its not prefect it normally gives a good indication

6.5 creedmoore 140gr amax.

2213 46.88gr for 60184psi. in a 28inch barrell propelant burnt =98.27% for vel of 2958fps.
drop it to a 20 in barrel and we get propelant burnt =95.85% for vel of 2738.
Load and chamber pressure remain the same

If I use 2209 (slightly faster) 44.74gr for 60211 psi
20 inch barrell propellant burnt =97.39% for vel of 2713fps


So with 2209 in a 20 inch we have a higher percentage of propellant burnt slightly higher chamber pressure but LESS velocity.