40 or 45 caliber for HD in a Beretta cx4 storm carbine?

[Auto-X Fil]

Something Pannone mentioned in a class to a buddy who had a 9mm AR was about having too long of a barrel. I don't remember if he said the magic number was 6 or 8 inches... But he said after that the bullet is out of gas and will lose velocity.

FYI, this happens around 12-18" for 9mm, depending on the exact load.

Now, velocity gain past 6-8" is pretty much nil. You literally get only about 50fps going from 8" to 16" with most 9mm ammo.

And yes, 45 is similar. It's actually even more tapped-out by 8" in most cases, due to the low pressures and large bore.

[mig1nc]

This should answer the velocity question. http://www.ballisticsbytheinch.com/


Sent from my SM-N920V using Tapatalk

[T2C]

When I owned a Colt 9mm with 16" barrel I chronographed Winchester 9mm +P+ 115g JHP. When fired out of a S&W 5904 with 4" barrel Average Velocity was 1,340 fps. When fired out of my Colt carbine Average Velocity was 1,638 fps. For this particular load a 12" increase in barrel length increased muzzle velocity by 288 fps.

I currently own a lever action .38/.357 rifle and compared velocities of ammunition fired from the rifle and one of my handguns. I fired Winchester .38 Special +P 110g Silvertip out of a revolver with 4" barrel and the Average Velocity was 942 fps. When fired out of the lever action with 20" barrel Average Velocity was 1266 fps. A 16" increase in barrel length increased muzzle velocity by 324 fps.

I think you reach a breaking point at which you do not pick up more muzzle velocity with increased barrel length. In my opinion there is no advantage in barrel length longer than 16".

[mig1nc]

Yeah, if you look at the graphs on that link I posted, with most pistol calibers you are done at that point. In fact, a pin and weld job on a 14.5 would be about optimal without needing a stamp.

Sent from my SM-N920V using Tapatalk