I ordered and assembled a bunch of CMMG parts and receivers for a 9mm radial delayed blowback project only to find the 9mm ARC Pmags wouldn’t lock. The problem seemed to be the 1st upper which I sent in and they confirmed was out of spec. It took them a month to send upper #2 that is seemingly used as it has what appears to be a lapped receiver face (WTH?). Either upper #2 is out of spec too and/or the lower out of spec also as it still doesn’t work! So, I’ve stripped the lower to send it and the the upper back. I put the mag catch and receiver pins in for the video. So, multiple out of spec parts, “new” parts that appear used, and slooooooow turn around time too! Wish I never started and just want to wash my hands of it.
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