I've measured hundreds of USGI M14 bolts, besides wear, they were all -pretty much the same (unlike M1 Garand bolts) except, Winchester M14 bolts.
Winchester bolts usually fit, with acceptable, snug headspace, in Chinese receivers with Chinese barrels.
When changing barrels, USGI bolts are easily used.
The receivers are very close to US specs, but the barrels are bolts differ.
The original semi-auto Chinese receivers did not look like GI receivers at all.
The importer was disappointed and claimed the first receivers were dangerous and recalled them from the distributors.
The Chinese M14 parts are surplus parts from the 1960's.
The first receivers may have been made of the chromium steel used for AK receivers.
The later, "stronger" Chinese receivers have the correct look and made of a modern, stronger steel.
USGI receivers are made of a chromium - nickel steel.
The first Chinese semi-auto receivers were round on the scope mount side, with a non-threaded hole with a large Norinco logo and possibly blued (very shiny), not Parkerized.
The importer didn't want those to represent the imports and recalled them, claiming they couldn't pass proof firing.
In Canada I saw the early Chinese M14 imports had the original select fire receivers, with the selector lug machined off of them.
The remaining US imported semi-auto receivers were made of better steel and retained the GI look, in shape and finish.
Canada also got new semi-auto receivers later too.
The US did get some, "law enforcement" select fire Chinese M14's imported.