Just a quick observation on a subject that has been posted many times, i have been a mechanic/machinest for 25+ years so i know a bit about fitting and measurements. i have 2 identical barells (same chamber and manufacture) and 2 BCG’s (same manufacture) both sets new and unfired. did headspace check with both BCg’s in both barells and on one of the combinations the bolt closed on the no-go gage with firm thumb pressure, being the currious type i put a thin piece of paper on the bolt face and re did, the bolt would not close on the no-go. the differance was .0015, all combinations passed on the go, and field test. So i would feel confident using any of the combinations, just wanted to point out that in manufacturing and machining every thing falls within a spec, + or - of the optimum so even parts that are individually within spec can some times assemble
slightly out of tolerance. still GTG.
Yes many things slip through QC. Most bolts work fine. Look at all the crap companies producing ARs.
Welcome to M4C.
Have bothered to read other threads that specifically address this? There is a current one right now.
Also the gage you are using is .223 not 5.56 which can make a difference depending on what you have. The standard for the military calls for a Field gage and not Go or No Go.
I agree with you 100%, i use the Colt spec 5.56 field gage (1.4736) as the final word on these chambers, my intent was that based on years of experience that 100 parts off the same mill or lathe with the same tooling and set up will have some tolerance difference and still be within spec.