The MEGA barrel claims sub MOA so its chamber is CRAZY tight. The 762 Industries BCG claims to be National Match so its
tolerances are CRAZY tight. For example, a DPMS barrel and bolt face combo are .002" longer. The bolt face on my DPMS BCG is 0.124"
deep while the bolt face on my 762I bolt is 0.125 (I measure 0.126" but manu. says 0.125).
The result was that I couldn't close the BCG on a Forster 308 1.630" GO gauge, at least no without pushing hard and having no way to get it apart again.
Interestingly the bolt WOULD close on a Federal M80 7.62x51 cartridge. According to the specs 7.62x51 has a rim that is just a tiny bit thinner than .308 Win.
I filled a magazine with rounds and hand-cycled them through, letting the BCG slam home each time.
After I did that a couple times I WAS able to get the BCG to seat on a GO gauge but it was T-I-G-H-T!!
I did some test shooting. I had on big gardening gloves and looked away for that first shot!
Everything worked fine. The gun shoots beautifully and had no problems with 762 or a couple of AE 308s I tried. I can see little bits of NiB coating flecking off the
back sides of the bolt teeth but I image that is to be expected. Out of 40 rounds fired I had 2 failures to eject. Dunno why.
Spoke to both MEGA and 7.62 Industries and both seemed to think the above is normal. I told them both the story and they seemed to think just putting lead
downrange would cure the issues. Basically they just need to wear each other in (the bolt and barrel extension). The guy at MEGA said 500 rounds.
FYI, it is definitely the 762I bolt that is tight. If I put a DPMS bolt in the 762I carrier it seats easily over a GO gauge. Amazing what 1/1000" will do!
Curious to know other people's experiences! Also curious to know if people think it's a waste to have a NM BCG in a 16" CQB/medium range MATEN. I could
put it in my Fulton Armory FA-10 22" Critereon instead and put the DPMS bolt in the MEGA.