The original bolts were made from 9310 IIRC and they switched to Carpenter 158 after bolts broke in the 50,000-60,000 round count range.
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50,000?
That's not TOO bad. I'm assuming rifle system.
I did a google search a few weeks back and it brought up an OLD thread on some Machinist forum where some bottom feeder was looking to find a sub for C158 to make bolts. :p
Seems C158 had been a tough find for a long time.
Here's the bcg I bought yesterday: http://www.americanspiritarms.com/up...rier-assembly/
I thought about buying a Phase 5 Tactical bolt carrier and then piecing some parts together to finish the bcg build.