11.5" Barrel Optimum Gas Port Size

[prepare]

Is there any data that even suggests an optimum size?
It seems companies are mostly unwilling to even share these specs...
With many shooters reporting over gassing issues it seems like the metrics companies are using to determine gas port size have more to do with ensuring cycling instead of actually determining optimum performance.

[Bob Sacamano]

Port size is a critical spec and should be disclosed. For a 10.5” carbine gas, .070” is “the standard”. 11.5” should be slightly smaller. I am not aware of any 11.5 barrels with a port smaller than .070”. Iirc, Colt sells a .070” 11.5” and Sionics sells their RGP barrel with a .071” port.

Either would be good choices to start. Order a few BRT ports then work down in size until you are happy.

https://www.m4carbine.net/showthread...-Gas-Port-Data

[MistWolf]

I have a Colt 11.5" upper with a .063" BRT Micro Port. It locks back without a suppressor.

[markm]

Is there any data that even suggests an optimum size?

Unsuppressed: .070" would be pretty good.

Suppressed: I'd probably run .063-.065"... I don't think my .063" 11.5 would lock back without the can unless I shot some smoking hot Black Hills 5.56 ammo. Anything weaker, and I was starting to lose reliability.

[BC98]

I've got a Triarc barrel with a .055" port that will cycle XM193 but not lock back on empty. Runs perfect with a can (Saker 556 and Sandman-K).

[Jwknutson17]

You will be fine in the low .062-4 range on an 11.5 with quality ammo, Auto carrier, and an A5H2.

.070/1 is too large for any suppressed only application.

I also have a 11.0 barrel with .0625 and it cycles with an H3 carbine spring, and also with an A5H3 Colt spring unsuppressed with m193 and mk262s. Doesn't lock back about half the time on empty mag unsuppressed.

[markm]

.070/1 is too large for any suppressed only application.

It's pure heaven unsuppressed though. That's my house gun.

[Clint]

And here I thought we were all talking about our new BRT 11.5" OPTIMUM CQB Barrel

[Furbyballer]

And here I thought we were all talking about our new BRT 11.5" OPTIMUM CQB Barrel

Gas port size? Why is this threaded for a 30 cal can and not a 556? When will it be available?

Sent from my SM-G950U using Tapatalk

[Bob Sacamano]

Looks good Clint. I see you have a standard and a suppressed option. What are ports for each? Wish they were 1/2-28. Its easy to get someone to recut 5/8-24 to 1/2-28 on SS, not sure on the QPQ.

Looks like these will be compatable with a standard FSB?