In the past couple of years, I've had a Ruger PC Carbine and a blowback AR-9. I parted ways with both of those for various reasons (doubling, OOB discharges, feed issues, harsh-for-caliber recoil, amongst others), and swore off straight-blowback PCCs for good.

I was looking at the MPX, but the pricing is crazy high. I finally got a chance to shoot one the other day, and while it was a nice shooting gun, I'm glad I didn't shell out the cash for one because it's definitely not $1100 better than what I ended up with.

I ended up ordering a CMMG "Guard" RDB bolt and barrel, along with an Aero Precision XL upper, and Atlas- S-One handguard. With the Endomag/CMMG 9mm conversion PMAG, it runs in a standard AR lower.

I finally got all the pieces assembled on Friday, and put about 400 rounds through it this weekend. This thing is SMOOTH! It's absolutely a night and day difference over the straight blowback AR9 I had. I was skeptical that the slight delay from the radial lugs would make that much of a difference, but having shot it I'm now a believer. Honestly, I'd put it right up there with the MPX I shot, and this gun is lighter and handier. I managed to clear a 6-plate rack in less than 3 seconds from 20 yards...which is really fast for me.

I shot some 124gr HST, 147gr HST, some WWB 115gr, some 110gr frangible, some flat point "mystery ammo" that my buddy had, and a bunch of my 135gr reloads. I didn't have a single malfunction. Even that goofy endomag design works flawlessly. Accuracy was ok...not precision rifle by any means, but acceptable for a PCC. I managed 2" groups at 45 yards with the red dot. It was most accurate with the HST.

I still need to put some more rounds through it to make sure no issues pop up down the road, but initial impressions are all good. If you're on the fence like I was, I'd say give it a shot. I don't think you'll regret it.

I have a Glock mag Guard and they are great guns, sitting in between the straight blowback guns and the pricier roller and gas delayed options, I can’t recommend CMMGs offerings enough.

Curious if you had doubling or OOB discharge with the Ruger. Mine’s been 100% so far.

quote:

Originally posted by 1KPerDay:
Curious if you had doubling or OOB discharge with the Ruger. Mine’s been 100% so far.

Nope, the only reliability problem with the Ruger was the second-to-last round FTF problem from my magpul pmag....no problems from factory Glock mags. It went away for other reasons (weight, excessive for caliber recoil, chintzy takedown lock ring, and the fact that you had to remove screws to take it down for cleaning).

The doubling and OOB were in the blowback AR.

The only known issues that I am aware of with the RDB is that early iterations would eat their ejector spring.

CMMG went to a much beefier spring and yours is new enough that it should have the upgraded spring.

But yes they are SUPER smooth shooting.


There is a big thread in the PCC subforum on AR15.com where guys run through all kinds of buffer weights, springs, etc. In an effort to get them to shoot as smooth as an MP5. The guy who started it says his is now even softer shooting than a MP5SD.

I've read some of those threads, and the hydraulic buffer sounds interesting, although expensive. Honestly I'm just blown away by how smooth this thing is as-is. I've never shot an MP5, but I'd put this rifle right up there with the MPX that I played with last week. If it stays reliable, I'm not sure what else I could ask for here.

Back when I put together my original blowback 9mm AR, this is what I was hoping to achieve, but it wasn't even close. At this point, the only thing I'm likely to change is the optic...the Strikefire II is bigger and heavier than it needs to be on an otherwise extremely light and handy rifle. I might go to irons, or something RMR-like, just to bring the weight down.

quote:

Originally posted by 92fstech:
I've read some of those threads, and the hydraulic buffer sounds interesting, although expensive. Honestly I'm just blown away by how smooth this thing is as-is. I've never shot an MP5, but I'd put this rifle right up there with the MPX that I played with last week. If it stays reliable, I'm not sure what else I could ask for here.

Back when I put together my original blowback 9mm AR, this is what I was hoping to achieve, but it wasn't even close. At this point, the only thing I'm likely to change is the optic...the Strikefire II is bigger and heavier than it needs to be on an otherwise extremely light and handy rifle. I might go to irons, or something RMR-like, just to bring the weight down.

Blowback is just so clunky and heavy and crude.

Neat bit of engineering from CMMG.

This message has been edited. Last edited by: IndianaBoy,

I wish I was as sensitive as the rest of you guys. My wife always says that too. I have every possible 9mm PCC operating system. Literally and in multiple versions. And when I shoot matches there is not a hoot of difference in my scores based on the type of operating system. Yea if I stand around and shoot a couple of rounds I might say yea the MP5 is better than the MPX is better than the CMMG is better than the Colt. But If you are running the gun it makes not a hoot of difference. If recoil is your problem go shoot a couple of serious .300WM rounds and you will be fine with whatever 9mm you pick.

quote:

Originally posted by hrcjon:
I wish I was as sensitive as the rest of you guys. My wife always says that too. I have every possible 9mm PCC operating system. Literally and in multiple versions. And when I shoot matches there is not a hoot of difference in my scores based on the type of operating system. Yea if I stand around and shoot a couple of rounds I might say yea the MP5 is better than the MPX is better than the CMMG is better than the Colt. But If you are running the gun it makes not a hoot of difference. If recoil is your problem go shoot a couple of serious .300WM rounds and you will be fine with whatever 9mm you pick.

I kind of want to say something snarky here, but I'm afraid I might find out that you are a USPSA Grand Master.



Not everyone can capitalize on the advantages of a rifle or PCC that shooters flatter.

It's not about recoil, it's about minimal sight disruption when you are shooting fast.


It's the difference between clearing a plate rack in 6 seconds or 3 seconds.


Maybe you are so good that you can run a direct blowback 9mm AR just as fast as a MP5 or MPX.

Or maybe your scores are the same because you don't run either of them particularly fast.



I don't want to make assumptions about your shooting abilities because you may indeed be a USPSA Grand Master and I should slink off to a corner.

And maybe some of us aren't recoil pussies, or similar in strength to your wife, who need time behind a 300 WM to understand what recoil is, and we are fast enough to capitalize on reduced sight disruption.

quote:

Originally posted by 92fstech:
I've read some of those threads, and the hydraulic buffer sounds interesting, although expensive. Honestly I'm just blown away by how smooth this thing is as-is. I've never shot an MP5, but I'd put this rifle right up there with the MPX that I played with last week. If it stays reliable, I'm not sure what else I could ask for here.

Back when I put together my original blowback 9mm AR, this is what I was hoping to achieve, but it wasn't even close. At this point, the only thing I'm likely to change is the optic...the Strikefire II is bigger and heavier than it needs to be on an otherwise extremely light and handy rifle. I might go to irons, or something RMR-like, just to bring the weight down.

The problem with hydraulic buffers is that they are prone to breaking.

Not a huge problem on a race gun as you can change them out at a regular interval, but they are expensive and I don't really want to throw that much money at a gun to keep it running.

It all depends on if you are willing to keep buying them at regular intervals.

quote:

It's not about recoil, it's about minimal sight disruption when you are shooting fast.

This. Very much this! I have a .45-70, so I know about recoil. It's not like any 9mm PCC produces heavy recoil, but there's a certain expectation of light, smooth operation that comes with shooting a tiny pistol cartridge out of a rifle platform, and the bounce and sight-hop I experienced with my blowback guns made them harder to shoot fast than my .223 AR.

This CMMG system feels more on-par with my .223, and possibly even smoother and lighter...which is what one would expect when shooting a smaller, slower cartridge out of a comparably-sized platform. I attribute some of that to the radial delay, but I think another significant contributor is the lighter carrier and buffer that the system allows, which results in less reciprocating mass.

Add to that that this gun hasn't doubled or grenaded any brass in my face, and it results in a much more enjoyable shooting experience.