11.5” Colt FBI Barrel Ejection

[OldState]

Searching for something to measure but I will post it.

The barrel is a legit heavy FBI profile colt sealed in a blue bag. I’m just hoping that it was ported the same as others in the market.

[Clint]

Any updates on this?

[OldState]

Got sidetracked with a few weeks of travel for work on top of packet weekends. Also got discouraged looking for pin gauges to measure. I’m leaning heavily toward just getting one of your gas tubes but I would like to know the actual size of the GP.

[556BlackRifle]

In addition to the excellent gas port advice above, check out the Vltor A5 H2 with Springco Green. I find it to be a very forgiving combo.

[bigkracka]

From personal experience AU is shady at best. The HRT barrels are not exclusive to AU.

[OldState]

Well to be specific they said the HRT barrel with the shaved FSP were exclusive to them. I have know idea if it’s true or not.

[Clint]

Sent a couple old drill bits your way to get this figured out.

Searching for something to measure but I will post it.

The barrel is a legit heavy FBI profile colt sealed in a blue bag. I’m just hoping that it was ported the same as others in the market.

[Clint]

Just received an email from a customer with three of these FBI barrels from AU.

He measured the ports with pin gauges at 073.

This would explain the hot cycling.

Built my first pistol upper. I bought a 11.5” Colt Heavy Commando barrel from Arms Unlimited. Came with shaved and pinned FSP gas block from Colt. AU claims this is an FBI HRT overrun.

Went with this barrel because of its reported .069 gas port and accuracy. Also the price was great. Swapped out my unfired 16” barrel from a new 6920 I bought a few years ago...so upper, barrel, and BCG are all Colt.

I wanted a properly gassed rifle for 50/50 suppressor use when I get that. Using a H2 buffer from SOLGW and the Colt buffer spring.

Fired Federal XM 193 and the rounds are ejecting at 2 o’clock about 3-4 feet away with a slight but noticeable ding on the cases from the brass deflector. Fiocchi .223 ejects at 4 o’clock as does Brown Bear .223. No dings.

With an H2 buffer and a .069 gas port I didn’t expect the ejection pattern from the full power ammo. I didn’t have a way to measure the GP when I had the GB off to put the rail on.

Is this normal? Seems like it’s cycling pretty fast with FP ammo for a .069 GP. I understand ejection patterns have a lot of variables. Recoils feels similar to my 16” 6920.

[OldState]

Sent a couple old drill bits your way to get this figured out.

Thanks so much!

Just received an email from a customer with three of these FBI barrels from AU.

He measured the ports with pin gauges at 073.

This would explain the hot cycling.

Interesting. So if that turns out to be the case with mine, what size gas port/tube would you recommend? Would like it to still be able cycle Brown Bear, etc.

If the Crane spec for 10.5”s is .070 shouldn’t 11.5” be a bit smaller? Thanks!

[Clint]

.069 is a good size unsuppressed.

50/50 mixed can be smaller.