Our MkG GUARD Barrel and BCG Kit allow you to build a Pistol Caliber Carbine using our Patent Pending Radial Delayed Blowback System. Unlike typical direct blowback systems, our RDB uses a bolt that is forced to rotate and unlock, slowing the BCG. This results in a lighter BCG for a lighter rifle, and less felt recoil than a straight blowback system. Our MkGs Barrel and Bolt Kits are designed to work exclusively with our MkGs Lowers. Other manufacturers lowers may work, but we cannot guarantee function or reliability. Buy a new 9mm AR barrel today! Specifications for CMMG, Inc 9mm Barrel and Bolt Carrier Group (BCG) Kit: Manufacturer: CMMG Color: Black Finish: Salt Bath Nitride Fabric/Material: 4140 Chrome Moly Cartridge: 9mm Luger Gun Model: CMMG MkG-45 Guard Threads per Inch: 1/2×28 Barrel Twist Rate: 1-10 Condition: New Package Contents: CMMG, Inc MkG Guard 9mm Barrel and Bolt Carrier Group Kit
Gromit –
I shoot steel matches and have been using the typical blow back 9mm PCC. Once tuned, they work good as long as you keep them clean and don't mess around with the PF too much. To use the CMMG setup I installed the 9mm CMMG upper on my AR15 lower (stock spring and 3oz buffer) and used a standard PMag with a 9mm conversion kit installed. The gun ran great! Very little recoil at all and ran several different brands factory of ammo without and problems. I also tried some hotter hand loads and it did make a difference as to where the brass landed. As with an AR15, you should adjust the buffer weight to fine tune it to the load you plan on using. However, it ran factory ammo great.
Padden –
I installed this kit in a mil-spec (recommended by cmmg) upper to use with cmmg’s arc-9 mags. A little over 400 round through it so far in various weights and manufacturers including browning 125 round nose, Winchester white box, and 147 Remington. 100% function both suppressed and un-suppressed. Highly recommend this product.
Blue-collar –
I pick up this CMMG both barrel kit to build my AR9. I pick the 8 inch barrel. High quality, the Bolt and bolt carrier group is perfect. They have a spring behind the bolt and a round cam pin. It’s a little different but other than that it is perfect. I highly recommend this product
BB –
I built the 8" kit into an Aero Precision Receiver/Handguard, Stealth Recoil Spring, and SB PDW brace. Out of 500 rds, we had one failure to eject, but the round sounded weak when fired, so we weren't surprised. No squip, fortunately. The recoil is light, even for my 78-year old mom who loves shooting it. It's cycled all kinds of brass and steel case, as well as hollow points. I highly recommend this system.
Jerbear –
If you're looking into buying this, you know what you're looking at. You're attempting to build a PCC with certain characteristics that a direct blowback gun uses heavy buffers & springs to control. Well, it works! It's lighter than your typical blowback bolt & seems to stay cleaner. I just broke mine in today by putting 100 rounds through it. CMMG opens up the ejector port on the Guard & Banshee so I watched for signs of brass hitting anywhere, none found. All of my brass ejected cleanly. CMMG also has a "shelf" milled into the magwell that prevents over-insertion of the magazine, keeping the mag from coming into contact with the bolt. Lesser manufacturers rely on the ejector to limit the height of the magazine in the magwell. The ejector is built into the bolt face like it would be in a standard AR, so the ejector needs to come out of your typical 9mm lower. Just a few things that I came across during my build. It was worth it for me, I couldn't be happier with these parts. I'm just running a standard carbine buffer and spring, that's what CMMG runs in the Guard & Banshee from what I understand and unless I have any issues, that's what I intend to stick with.
Ricky Bobby –
Bought the 8".First bolt self destructed. At first Customer Support said the wear was normal. The bolt had chunks on the leading edge of the bolt missing. This is after 300 rounds. I sent pictures after multiple calls, I sent photo's and they reluctantly agreed to issue an RMA. A week later I followed up with them and yep the bolt was shot they will send me a replacement… toughly a month for this.The whole time the gun was a jam-o-matic. Couldn't get through a magazine without jamming. I figured it was the bolt.When the replacement came in, the gun still jammed 1-10 in with each magazine… I called the tech line multiple times, tried everything they said and still nothing. Finally after blowing through 2,500+ rounds testing (not a typo) they sent me an RMA…They said it runs fine. I asked if they were testing in a AR upper & lower? They replied no in our upper and lower, and now we have a disclaimer stating we do not guarantee function in anything but their upper and lowers. Well that would have been nice to know prior to purchasing.When they returned my barrel/BCG if figured I had nothing to lose and polished every surface that the round would come in contact with. That fixed the problem. Now that my gun has quite a few rounds on it I asked if I could buy a spare bolt since the one now is high mileage and when it was returned to me came back with significant marring on the lug face. Sales said no, the tech support said yes for $299… First and last product I buy from CMMG.