Re: Barrel length for slow buring powder
Is the barrel long enough for what?
Same or higher velocity from more slower powder?
Accuracy that doesn't degrade from excess muzzle pressures?
It starts with a bullet, it's weight and twist requirements, and case capacity needed combined with given powders to drive the bullet to needed MVs.
While shorter barrels are stiffer -all else equal, internal ballistics is still a dominant contributor to result.
While I couldn't prove it, I'm sure there are better barrel lengths than others for each internal ballistic combination and application.
But it would be a massive undertaking to produce a formula that passes all tests. We won't see it in our lifetimes.
In otherwords,, try it & see