Subsonics out of 16" unsuppressed

[Foster]

Anyone had luck getting their 16" upper to cycle with subsonics unsuppressed? While waiting on my form 4 to come back I wanted put some rounds down range and since subs are a whole lot cheaper (not finding any brass either) I have been using them. I put a Noveski KX3 flash suppressor on which helped. I only have 200 rds through the upper and I am hoping that by the time I hit 4-500 rd it will be reliable. Accuracy - no problem! 1/2-3/4" @ 100 yds.

[LeftEyeMike]

Sounds like a gas port size problem on the barrel.

[SuperChuck]

I have the 16" pistol length gas port, and it cycles subsonics(Remington 220 grn) fine with no can, I assume that with a can the performance would be comparable.

I've tried to use some lighter subs(150's) that did not cycle the bolt.

SC

[Foster]

Mine is a carbine length gas system. Still waiting on the stamp for my can so I do not know if the can will clear up the issue. I am holding off contacting CMMG until I have tried it with the can.

[rnd]

Mine is a carbine length gas system and it cycles subs just fine unsuppressed.

[Hooz]

[L1A1Rocker]

That chart would indicate that their barrels cannot do what other 300BLK barral manufactures can. Simply, run both supersonic and subsonic ammo. Which of course, was one of the big advantages the 300BLK has over the 300 Whisper(tm). I wonder what the problem is.

[CMMG]

It's not that it won't work, it is just not recommended.

The supersonic ammo will be way over gassed with a pistol port.

The sub-sonic ammo with the carbine is simply not 100%, certain loads,buffers, bolts and weather conditions can sometimes lead to that configuration being a little under gassed.

[Foster]

Would increasing the diameter of the gas port increase the reliability of my CMMG upper when firing unsuppressed subsonic rounds or is this ill advised? The upper is very accurate but will not lock open on an empty mag., and will cycle a new round only about 15% of the time. I am waiting on the stamp for my can and would not do anything until after testing it with the can. I only have about 300 rounds through the upper so if you recommend getting more rounds through it before making any adjustment that would be helpful information as well. Thank you.

[L1A1Rocker]

It's not that it won't work, it is just not recommended.

The supersonic ammo will be way over gassed with a pistol port.

The sub-sonic ammo with the carbine is simply not 100%, certain loads,buffers, bolts and weather conditions can sometimes lead to that configuration being a little under gassed.

I don't believe this is an issue with AAC or Delta Company barrels. I am considering another 300BLK build on a 16 inch barrel. The price of the CMMG barrel is attractive, but if it cannot perform reliably with sub and super sonic ammo I'd be looking at having to use variable gas blocks/tubes or such that are used to make the Whisper reliable. Part of the appeal of the 300BLK is that these "tricks" are not needed.