So not a clone and not tacticool. But here is where Im at.
CMMG lower but the upper is almost all Colt. My intentions are to replicate an R6450 9mm.
The charging handle is not Colt and I cannot verify if the skinny 6 hole hand guards are Colt.
Im not going to put on the cool aluminum CAR butt stock. Its just not the right time frame for
this build. 1985-1987. Im keeping my eye out for a Colt N1..for cheap. The mag catch and release
button are on my other 9mm. Ill be swapping them out shortly    
Im looking for some input.
Ejection port door. Should it be an A1 or an A2?
Headspace. With a depth micrometer. My bolt face depth measures .130" my chamber, .635".
That comes out to .765". With a case, trim to length of .751" It would seem my chamber is a bit deep.
Any input?



Notice no hole for a gas tube.

Your measures is skewed badly,,

Nominal case length as sen on market is 0.743" to 0.748"..  you state you measured bolt face at 0.130" ??   This will have you needing a 0.140" case stick out of barrel using a 0.744 case.. This will insure shorter case ammo still get sammiched between bolt face and chamber firmly for extractor to snap into groove and fire pin to firmly spank the primer