I’ve come a ways to get to where I am now, meaning after lots of wishing/searching/planning, I am wanting a 300 AACBLK for my next gun. Basically I’ve got a pile of parts from a few projects, not enough to put together into an complete weapon. So, I want to get the remaining parts and build one. I’ve done some research, I understand that the barrel and gas block (and possibly gas tube)are the only parts I need to swap from 5.56 to 300.
But the research I have done has left me confused as to which gas system to use.
Part of what got me to this point is the desire to have a suppressed weapon. I am planning a 16" barrel, and suppressor, no SBR’s. I want to be able to shoot subsonics and supersonics through it. I would rather not have to adjust gas blocks when switching between the two. I want to use this for hunting as well as just fun plinking.
So the question is what would be the best gas system?
I can’t help but think that close range suppressed hunting for deer, hogs, and coyotes would be a blast.
Pistol gas without question, if you are going to be shooting subsonics. They run much more reliably in a pistol gas system. If you are shooting supers, it doesn’t matter. However, even with a pistol gas port on a 16" barrel, everything is A-OK if the port is sized properly or used with an adjustable gas block. Some may say it is way overgassed but I’ve not found that to be the case.
FYI I have had both carbine and pistol gas barrels, and kept the 16" Noveske setup mentioned above (pistol gas, H2 buffer). It runs like a clock and is very accurate.
I noticed CMMG list the barrels at 16" with pistol gag system at Midway state in the discription: Suitable for use with Subsonic loads, either Suppressed or Unsuppressed
Use of Supersonic loads is NOT recommended with Pistol Gas Port Location
1/7 twist and pistol gas no matter the barrel length is IMO the IDEAL setup, although there arent a ton of barrels out there setup this way.
If you get a carbine gas’d barrel just make sure you open the gas port to .110 or .125 before putting the gun together. You can’t over gas a 16" carbine gas barrel.
I would say a majority(90%+) of issues with the 300BLK not running is traced back to a gas port that is to small.
Now on to the CMMG barrel. On paper their barrels look ideal: 7 twist, pistol gas, nitride coated, good price, etc… BUT they have been known to have VERY tight chambers and a lot of people have had issues with them with factory ammo. 300BLK isnt as easy to ream out like a tight 5.56 chamber is.
I couldnt tell you, but its from CMMG and while they THINK they are the experts on all things black rifle, they are far from real experts IMO having been to their shop a few times.
If shooting supers through a pistol gas barrel was bad or dangerous or anything else, you would think AAC, Noveske, etc… that make pistol gas 300BLK barrels would also have a caution statement, but they do not.
I am wondering if CMMG thinks it will over gas the gun? Its pretty hard to overgas the 300BLK due to how fast the pressure bleeds off due to the .30 cal bore as well as the fairly low powder capacity of the case. I think anything beyond carbine gas will hardly even run.
Now that the gas length has been set at pistol, that opens up lots of options on barrel length. Another dilemma!
Assuming I permanently attach a suppressor to bring the barrel length over 16", and assuming a Form 1 home build suppressor, what barrel length would be ‘best’ for running both subs and supersonics?
Im not really going to comment on “perm attached cans” except to say I think they are a terrible idea, but you can do your own research on that.
And building a Form 1 can, I hope you have a mill, lathe, etc… to build something that will be decent and work well. But again, I wont really comment on that as I am not a can builder.
BUT if you are sending off forms for a home built can, why not send off forms for an SBR at the same time and then you dont have to worry about perm attaching a can.
Back to your barrel length question. I have run a 9" AAC as well as an 8.2" Noveske pretty extensively and havent had any issues with either.
yes. I have a lot more time on the AAC than the Noveske, but the 9" AAC has eaten everything both suppressed and unsuppressed.
The 300BLK is VERY sensitive to gas port size. AAC spent a LOT of time in R&D to get it just right. I think Noveske has also spent quite a bit of time getting it right(although they do say theirs MAY not cycle subs without a can). Most other manufacturers dont have properly sized gas ports, especially when you get into the lower priced barrels.
If you have the manufacturing facilities, the integrally suppressed 300 BLK with a shorter barrel is not a bad idea. I would not do it though since I share my can between multiple hosts. For something like that a 8.2-10.5 in barrel would be perfect. Just remember the legal ramifications if you decide to remove it. I have successfully made the can that is on my 300 BLK via a Form 1, and it works well. It is hard to match the combination of performance, weight, and durability of factory made cans like AAC/Surefire though unless you are quite skilled at machining/welding. I did save a lot of $$$ however.
I wouldn’t worry too much about the CMMG warning, I have fired my Noveske pistol gas a fair amount suppressed + supers. I do put in an H3 buffer just in case. No harm has resulted from it, and it does not seem anymore overgassed than my friend’s DPMS AR in 223 (in terms of recoil + ejection pattern).