Thread: Myth? - shorter barrel = use faster powder?

Originally Posted by Micky Duck

if you take it to extreme ...or go backwards in time...or both... black powder achieved better burns with long barrels..... folks used to TUNE a load by shooting over snow,and keep reducing powder charge till no unburnt powder exited muzzle..... sort of the same as muzzle blast thing... my old 20" 270 had one heck of a muzzle blast and big ball of flame on dark with factory loads...feed it heavy projectiles,not so bad.
a faster powder that has completed its burning inside barrel wont waste energy on muzzle blast/fireball.....

Issue is it procuces gas so quickly it has to stop producing as earlier meaning as the bullet travels down the barrel this means pressure drops quickly. The slower powder takes longer to reach peak pressure but by that time it has more volume to create gas in and the pressure stays higher in the later portion of the shot cycle
slower powder needs longer barrel to complete its burning...same as black powder.... if you dont burn it all in the length of barrel you have,you may as well reduce the charge until you do,BECAUSE you wont make projectile go any faster with more powder....I BELIEVE this is the flat spot folks look for on ladder testing???
or very similar....

Definitely not true. the les powder added the less efficient the powder burn due to lower pressure. Powder burns much more readily at higher pressures (higher heats). Ie running data in QL 40 grains of varget gives me a 91% powder burnt whereas 48 grains gives me 98% thsi is due to the more efficiet burn at higher pressure. This is part of why the 277 Sig Fury is so efficient (135grain 2777 at 3000fps from a 16 icnh barrel but runs at 85kpsi vs 65ish for most cases

shotshells use a very fast burning powder and short barrels still produce horrendous fireballs,maybe the lower pressure plays part??? ...long barrels are much nicer to use and as bonus take the bang further away from your ears.

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