Pistol Calibre Carbines

[MirandaV]

I was wondering about the if there is a difference in performance with a rifle vs a pistol in the same caliber. From what I read on here, shortening a rifle that uses a rifle caliber will lower performance quite a lot in some cases, due to unburned powder, etc. Would a rifle using a pistol caliber enhance performance? Or would it not because there's not much powder left to burn as it is made for the shorter barrel of a pistol?

[geologist]

It depends on the cartridge.

Magnum cartridges like the .357 Magnum, .44 Magnum and the .454 Casull are MUCH faster from 16-20" carbine barrels than from a revolver with its cylinder /barrel gap. So much so that you should choose a sturdy bullet for use in the carbine due to its much higher velocities. You don't want the bullet to come apart before you get sufficient penetration.

[Grawfr]

Just as Geologist said. Shooting the bullet out of a 18" barrel gives the expanding gases more time to act on it, and you end up with 200-500 feet per second extra muzzle velocity compared with a 5" barrel (depends a lot on the caliber used!). There's a good site where this was documented, called Ballistics By The Inch: http://www.ballisticsbytheinch.com/

There's a practical limit where the bullet actually begins to slow down in a long barrel, usually around 17" to 18", but that's still faster than what we would get out of a 5-6" barrel.

[MirandaV]

So something like a Mares leg in a magnum?

[jparent]

I believe the standard semi auto calibers (9mm, 40, 45) max out and would be perfect with a 12" barrel. Of course with our silly laws, we are stuck with 18+ and slower velocities.

The magnums, 357, 44, etc and 10mm benefit greatly from a longer 16"-18" barrel.

[Gatehouse]

There is no question that adding barrel length will increase velocity, although at a point it becomes diminishing returns, especially with small cases such as you will find in a pistol cartridge.

I've used a few pistol carbines, and you can see an improvement- For instance, a hot loaded Colt .45 in a 16" barrel will give you the same velocities as a .454 in a 6-8" barrel. And while I have never bothered to chrono it, a 9mm in a Beretta carbine will definitely increase velocity. I have gauged this in a very unscientific manner- When I hit a gong at 100m with a 9mm from a pistol, the steel gong makes a "tink" and barely moves. Shooting it with a Beretta carbine, and it starts swinging. Not compared to hitting it with a .223 or 7.62, but there is a clear difference.