10.3" range report with unmodded gas port

General Firearms NFA
1

All the trends lately have been leaning towards small as possible gas ports if running 100% suppressed. I had a Colt 6921 upper laying around and decided to have it chopped to 10.3" without the gas port being opened up. I sent it to Adco and had it back in 6 days, kudos.

I put it back together over the weekend and went to the range today to try it out.

Specs
SBR LMT lower
H2 buffer
Relatively worn factory recoil spring (4,000-5,000 rounds)
BCM BCG
Colt 6921 upper cut to 10.3 with UNMODDED gas port (factory gas port, not sure on size)
GemTech HALO
M193 ammo

I first fired 5 rounds into paper to double check that there was no keyholling etc… All was well here so I decided to move on with testing. The first 5 rounds all fired and cycled fine without the suppressor, cue my surprised face. I really didn’t think it would cycle with the unmodded gas port. I finished the mag (un-suppressed) and it locked back on the last round, cue second surprised face.

I then attached the can and ran a few mags through it. All functioned 100 percent and it was pleasant to shoot. I know Gemtech doesn’t rate high on the Gucci scale (I have other cans) but I was pleased with how it did on the shorty. I built this upper to run 100% suppressed and this can will “live” on this upper for the most part now. I realize this is a small sample but it’s a start.

I will update this thread in the future as time allows me to get to the range and report back on results.

ETA: OMG my Colt upper is purple…I just saw this in the picture…what will I ever do…lol! :sarcastic:

2

So what is the current gas port size on this upper? What ammo were you shooting?

3

Very important details that I left out, thanks gunz.

M193 and factory colt gas port. I think I have read they are .062 but I don’t have the tools to pin gave it.

4

Good post.

How many rounds were through the upper prior to cutting it down? Any possibility of it having port erosion before you cut it down?

5

The upper had been through one carbine class, so aprox 1300.

When I took it apart I could not see any erosion, I doubt that there would be much at all after only 1300 rounds.

6

Looks very familiar :wink:

When you say it was pleasant to shoot. Meaning how? Any “gas face”? How was recoil both before and after mounting the can?

I still haven’t taken mine out, but my can or SBR stamp haven’t been approved yet so I don’t see the point.

7

Gas was very minimal. I run my guns pretty wet with Slip 2000 and to me it seemed not much different than without the can. Recoil was basically the same, cans don’t stop physics but to some shooters it seems to reduce “felt” recoil.

ETA: Interested to see your results, IIRC you were cutting down a 16" DD barrel…?

8

Yes, its already done I’m just waiting on the ATF for both stamps.

From what I’ve read it either has a .062" gas port or a .058" gas port. I never measured it beforehand, I don’t have the tools to do so but I have read many accounts of people with non CHF 16" DD barrels having different port sizes. I will try it out unsuppressed with an H and H2 buffer, commercial .223, Wolf .223, Federal M193 and M855.

My main concern was not having gas in my eyes when firing suppressed, and it sounds like in your setup that issue is solved.

9

:eek: Uh oh! A constructive intent upper! :fie:

10

INDEED!!! That thing should be kept at least a city away!:sarcastic:

11

Of course you bring that up…in the one thread I’ve ever made about this without mentioning that I have a pistol lower for it. :neo:

But yeah, the ATF agent accompanied the UPS Driver when the barrel was brought back after being chopped down. He inspected my house and I showed him the lower. I’m off their radar.

12

M193 is hot ammo and the GP is most likely .063.

Try some .223 ammo and see if it locks back without the can.

C4

13

I’d like to see this as well. I’ll even send you a few boxes of Wolf mil classic 55 gr. .223 to test.

14

Thanks for the report! I’ll definitely be following the testing that you put it through…very nice!

15

If you send it he will shoot it…lol

Would be an interesting test to run it with H buffer and Carbine buffer…

I only run hotter “milspec” ammo as an fyi.

16

Then PM me with your address.

17

Wait, this is a joke right?

18

I was wondering the same thing.

19

I should be able to get out this weekend or next and test some wolf ammo unsuppressed. I will try it with an H2, H, and carbine buffer. I will be checking for cycling issues and lock back on an empty mag.

I’ve never shot wolf so this may be interesting

20

:stuck_out_tongue:

I’m guessing it was