Saw the CMMG MKGs 9mm radial delayed blowback upper. Uses an adaptor in Pmag bodies so can be used with any standard AR15 lower.
Anyone have any experience with this setup?
OFG
The CMMG delayed blow back uses a bolt very similar to a regular AR15. (for those that do not know) . With that, the ejector is built into the bolt face.
Most of the 9mm AR's (PCC's for some people) are straight blow back and the ejector is on the receiver (lower). (again for those that do not know)
This comes into play because on the EndoMag adapters the ejector is built into the adapter. Mean arms the maker of the EndoMag adapter is who is making the adapters (or CMMG is licensing their product/patent). When you get a adapter from Mean arms it comes with instructions on how to remove the ejector, or when you order there are instructions to put in the notes you are ordering for a CMMG upper and they will remove the ejector from the adapter for you. This is what CMMG is selling.
The modification to the adapter is permanent, so once done it will only work with a CMMG upper.
With all of that I have dedicated glock SBR and I also compete in USPSA matches. I shoot pistol but watch the PCC guys and let me just say Glock dedicated lowers are just not 100% reliable. 2 or 3 have issues every match. The JP guns are the most reliable but still not 100%.
Alot of the issues involve the BHO and many guys remove them. I will say if my SBR BHO screws up one more time I am shit canning it. I think I have it figured out, but alas I have not shot it for months and you are about to find out why.
When the EndoMag was announced last year I instantly thought "that is the answer". I was one of the first to order. It took a few months for the initial production to get up and running.
When I received them I took my Glock SBR upper and put it on a standard AR15 lower (also registered SBR) to experiment with. I figured if they did not work I was only out $80 before I built and entire gun around the EndoMag adapter.
I had one small issue and that really has to do with the huge tolerance differences between 9mm AR bolts. With slight pressure on the mag (any direction but down) the bolt would hit the ejector and stop its forward motion. If no pressure was put on the mag, mag was allowed to "float" and move in the mag well as it wanted it was 100% reliable. I put a little over 1000 rds through it this way and had 6 incidents as described and everyone was when I touched the mag. The BHO operation was awesome.
Doing some research some ejector cuts in 9mm bolts are not as deep as others. So feeling the adapter was GTG I built a gun around it, I just made sure I used top quality parts.
Understand the issue above would not be an issue in a CMMG because of its built in ejector.
I used an Aero Precision lower, and a FoxTrot Mike side charging upper. I built it as a pistol and have over 2000rds through it since Christmas 2018. Not one single failure. In fact about a year ago I was reloading 9mm and set my COAL to short. I ended upp with a little over 100 of them. They would not feed in any of 3 pistols, nor my SBR so I put them on my shelf meaning to take them apart later.
Well a couple weeks ago I remembered them and grabbed the box when headed to the range. At the range I loaded 5 at first and the Endomag fed them flawlessly and functioned perfect. I loaded 10 next and same thing. So then to finish them off I loaded 3 mags (90 rds) and not one single issue. I tried to make it fail and it won't. Personally I am sold on them.
Using for USPSA comes with a couple issues, some glock mag adapters allow almost 50rds. So with only 30rds you will be at a disadvantage (personally think there should rules or different divisions for PCC).
The other issue (again will not affect CMMG) is some what of a safety issue if you have your head up your ass. Because the ejector is built into the mag, if you drop the mag with a round in the chamber and pull the charging handle back the extractor will pull the round out but there will be no ejector to kick the round out of the gun. The round will go right back in the chamber and you still have a loaded gun. Pull the trigger, BANG instant Shit your pants and DQ.
There are warnings with the EndoMag about this. Proper unload is pull charging handle back and either hold it back while dropping the mag or lock the bolt back with BHO and then drop the Mag. Verify Clear. This is the exact reason I went with a sidecharger when I built mine. I can put the "brace" (built as pistol remember) against my body, pull the sidechager back and have my right hand free to operated controls (mag release and/or BHO).
In my opinon the CMMG and the EndoMag adapter are the perfect match you will not be disappointed.
The "break in" video did not exist when I started the adventure but is a direct response to the issue I had (and others) with my SBR bolt. Again NO ISSUES with the FoxTrot Mike bolt.
