Gas port size: 14.5" vs 12.5"

AR/M4 Custom Build Forum
1

I’m thinking about having a 14.5" barrel cut down to a 12.5" barrel. Are the gas port sizes different for these two standard barrel sizes?

2

I asked Robb at VA Arms this same question recently. He suggested I have the gas port drilled out from 0.063" to around 0.071" or 0.073".

3

Someone here had standard LMT 14.5s cut to 12.5 for his agency and there were no port mods needed.

It would likely depend on the original port size and barrel I’d guess.

4

I remember grinch and dano also posting something last year about M4 barrels cut down to 12.5". Here’s the thread https://www.m4carbine.net/showthread.php?p=206714#post206714 .

5

Who made your barrel? If it is a Mil-Spec maker, you most likely have a .063-.065 GP size.

Assuming that you are NOT shooting the gun with a can on it, you will most likely run into an issue with the bolt not locking back on the last round.

An LMT Enhanced Bolt Carrier (no group) would most likely fix this issue.

C4

6

Thanks for the input guys. I found the linked thread interesting as well. The barrel to be cut down would be a Noveske 14.5" N4 Barrel.