The Myth of Barrel Length and Velocity Loss - Page 2

BlueTrain · February 20, 2012, 03:56 PM

With handguns, at least, it is possible to have higher velocities with a slower burning powder, in spite of the "inefficient" burning of the charge, meaning it continues to burn after the projectile is outside the barrel and "wasting" the powder. Faster burning powders may produce excess pressures in achieving the same velocities. While it is true that with a slow burning powder, there may be some waste, it is a case of efficiency being measured the wrong way, if velocity is what you're after and not economy of the propellant. But that's only with handguns.

I'm not at all sure that barrel length affects accuracy but it might affect the ease of aiming, again particularly with handguns. Everyone seems to use optical sights on rifles anymore, so it isn't a factor then.

brickeyee · February 20, 2012, 04:17 PM

Quote:

The perfect length barrel is one that is long enough that your powder finishes burning just as the bullet leaves it. If the powder burns before the projectile exits, friction slows it down. If the powder doesn't completely burn, anything left over is wasted.

Oversimplified to the point of being incorrect.

It is not about just powder burning, but pressure.

As long as the pressure behind the bullet is larger than friction losses the bullet will be accelerated by a longer barrel.
The powder finished burning long before that point.
The expanding high pressure gases can still do work.

Smokeless powder is almost uniformly under-oxidized.
There is not enough oxygen present to bring all the products generated to a stable cool state.
The muzzle flash is from the hot gases reacting with atmospheric oxygen.

'Flash suppressing' chemicals added to the powder are to provide more oxygen, but the down side is they reduce the energy density of the powder.

February 20, 2012, 03:56 PM	#26
BlueTrain Senior Member Join Date: September 26, 2005 Location: Northern Virginia Posts: 6,141	With handguns, at least, it is possible to have higher velocities with a slower burning powder, in spite of the "inefficient" burning of the charge, meaning it continues to burn after the projectile is outside the barrel and "wasting" the powder. Faster burning powders may produce excess pressures in achieving the same velocities. While it is true that with a slow burning powder, there may be some waste, it is a case of efficiency being measured the wrong way, if velocity is what you're after and not economy of the propellant. But that's only with handguns. I'm not at all sure that barrel length affects accuracy but it might affect the ease of aiming, again particularly with handguns. Everyone seems to use optical sights on rifles anymore, so it isn't a factor then. __________________ Shoot low, sheriff. They're riding Shetlands! Underneath the starry flag, civilize 'em with a Krag, and return us to our own beloved homes! Buy War Bonds.