Good question. From my understanding, the older TDP required that EVERY bolt and barrel had to be MP tested (after it was HP tested). The newer (revised TDP) apparently allows for batch MP testing.
To be brutally honest, the HPT/MP thing is really outdated. There are much better ways to check steel these days (like Xraying it).
I believe that it does.
Yes.
Here is the other dirty secret. If a company is NOT High Pressure Testing PRIOR to MP testing, the MP testing is virtually WORTHLESS as you did NOT stress the part.
The only companies that I am aware of that are HPT/MP testing EVERY bolt and barrel are:
Most every company shot peens their bolt (pretty common). Just got off the phone with Noveske. They HPT/MP test EVERY N4 barrel. They do NOT do that to their SS barrels. Also, their bolts are MP tested (only).
No, but I am pretty sure I know where. It is the same place the FN buys their bolts from. The company also holds the current USGI contract for small parts.
Do bolts that have “CM” stamped on them mean they were manufactured by Continental Machine?
ETA I’ve done some searches, and yes it does appear to mean Continental Machine. Some of my bolts I’ve purchased over the years from Bravocompany, Denny’s Guns/Global Tactical and Del-Ton all have the same “CM” on them. Hhhmmm…
