Minimum/Best Barrel Lengths for Various Auto Cartridges

[Higgins]

As I understand it, pistol cartridges lose velocity (effectiveness) when they are shot out of shorter and shorter barrels. That is, various semiauto cartridges need minimum length barrels to get the full effectiveness out of their size/load.

For instance, I've read that the best/minimum length for 10mm or .45 is a 5" barrel and anything shorter results in substantial losses in velocity/effectiveness thus undercutting the advantages of these cartridges. Also heard that at a certain point, a 9mm out of too short a barrel renders the cartridge no better than a .380.

So, what are the optimum/minimum barrel lengths for getting the full effectiveness/velocity from various standard semi-auto cartridges? (And how then can guns like ultra compact .45s and 9mms remain as effective as bigger pistols?)

In particular, I am looking at getting a 10mm. Many have a full 5" barrel, but some, like the one I am looking at has only a 4.25" barrel. So how much do I lose in that .75" difference?

 

[Sean Smith]

Generally, more powerful cartridges lose more velocity as you shorten the barrel, since they rely on larger volumes of slower-burning powders to hit those higher speeds. So a .357 Magnum will have a bigger ballistic advantage over .38 Special when comapring both from 6" barrels vs. 2" barrels. HOWEVER, .357 Magnum still has a considerable ballistic advantage over .38 Special from even the 2" snubby. The same would be true for autoloader cartridges... really short barrels make everyone's ballistics crap out, but the drop is usually more noticeable with high pressure cartridges than low pressure cartridges.

The "optimum" barrel length for a 10mm Auto is probably something like 10-14". More pressure more barrel more better. But even from a 4" barrel, it will stomp a .40 S&W into the ground.

So the short answer to your question is about 50-100 feet per second at the muzzle.

 

[PCRCCW]

There is no right answer..it is strictly ammo specific. Faster burning powders love shorter barrels....slower= longer. The Mag 357 is still spewing flames out of a 10" barrel gun..but gains little velocity over 6-8" lengths also....ironic.
The 50-100 FPS rule applies to most in the loss department.
Shoot well