Hi!

I'm thinking about building an integrally suppressed 9mm on a CMMG radial delayed system, that can be used both with and without the suppressor sleeve for competition.

My inspiration is the Brekke Custom CompXtension and several integrally suppressed 22s.

Is this doable or should I just forget about it? All input is appreciated.

(Due to my 2000 character limit I will follow up with replies)

For those that are not familiar, the Brekke Custom CompXtension is a pin/weld muzzle device used to reduce dwell time and is gaining popularity within the PCC competition community. It makes the barrel behave like a 10" while keeping the oal to 16". Also, since it is pinned and welded, it is no longer possible to use a suppressor.

Looking at the Brekke device, I see the resemblance to how an integrally suppressed rifle is built -with additional baffles and a sleeve. Which made me think: Can I have both? Are there any monocore suppressor designs feasible to be utilized in an integrally suppressed rifle -both with and without the sleeve mounted?

Pro: Quiet time with the sleeve on, competition time with the sleeve off.
Con: Hand/handguard exposed to muzzle pressure leading to discomfort or damage when the sleeve is off.

To question the con: 9mm muzzle pressure is pretty low compared to 223, but is it low enough to not be an issue in a design like this? The Brekke device starts as a 3-port upward facing brake, and thus the handguard is cut to let those gases escape. The rest of the device however can be tucked when a traditional HG is customized.

Worth noting is that where I live suppressors are not regulated and free to buy/make/use. Rifles, barrels, bolts and receivers however are regulated, and parts accessibility is somewhat limited. Barrel length needs to be 16" -SBR or pistol is not an option.


Some images for illustrational purposes. (please enlighten me if there is a better way to embed pictures, this is not what I had in mind)

SIG did something similar with early MPXs, got C&D'd by the ATF...

Your situation would be different, don't see why it would be an issue with a Form1 in place if the device was pinned/welded (unless you are OK with a 2 stamp gun)

ATF won

I am not under the jurisdiction of the ATF. Suppressors are perfectly legal for me to build or buy, but I have to comply with a minimum barrel length of 16".

What Sig did is pretty much exactly what I had in mind. It looks as though they added m-lok covers to the sides of the HG shield from the recessed muzzle blast.

Ah, wasn't sure if the country flag was factual...

Can you get a delayed blowback setup?  Hydraulic buffer?
Both of those will probably serve you better than an oversized brake.

I'd build 2 uppers, one integrally suppressed, the other with a solid 16" barrel, back-bored to ~10" if that is your goal.
Maybe add some porting if desired.

I have the CMMG radial delayed upper which is kind of delayed, if not as refined as an mp5 or jp5. I am thinking about a hydraulic buffer, but I heard from a few who tried the Brekke device that it was the most "game-changing" mod they did to their PCC setup. I believe it has to do with the dwell time as much as the compensator, which in turn should be more effective 10" from the chamber than 16".


If so, the suppressed wont be built in a while. Maybe after i do one in 22lr.