01-18-2018, 03:25 AM
Dcommoncents Wrote:I'm not remotely an expert so feel free to correct me, but I'm not sure what you mean by "mil spec" because I don't think that term has any real meaning in the context of chamber or bolt dimensions. I take it you are referring to the parts being made within the correct tolerances, for example the barrel being manufactured with a saami spec chamber in such a way that the cartridge will be properly supported at the shoulder and base when used with a true .136" bolt. Opinions obviously vary widely on the necessity of checking head space since it is incredibly rare to have an issue when the barrel and bolt are from established manufacturers.
Nonetheless, barrels and bolts are made by humans using machines with parts subject to wear and misadjustment, so checking head space is nice insurance against the possibility that either the barrel or bolt is out of spec, or both are slightly out of spec such that the errors compound to create a problem. Personally, I'm not exactly religious about checking head space -- I just stuck some layers of masking tape on the back of 2 cartridges to make a poor man's no-go gauge to "check" my newest grendel upper -- but I do think it's prudent to check every barrel/bolt combo whenever possible.
Masking tape no-go gauge. I like it.
If the specification on parts is set by the military it is "mil spec".
I mentioned Colt set the spec to .136" for the bolt face because that's what I read here and elsewhere.
I don't think this is mil spec since the military did not adopt the Grendel. Maybe it is "Colt spec".
Most people buy the group buy bolt specified at .136" and buy a barrel with the same spec assemble it and shoot and everything works fine.
I don't think there is an epidemic of mil spec parts being out of spec. I think the manufacturers do a very good job.