I've learned a lot from this thread. Guess I better start carrying a spare bolt in my bag-o-tricks. Thanks for all the great info!
Here is even a little more info, I thought it only fair to show what Bill Alexander replied in the 65grendel.com forum:
" Let me clarify this completely so that there are no misunderstandings.
- The bolt in question had a machining error present. In manufacture one of the cutters had broken and the operator had replaced it with a regular end mill rather than a radiused cutter. This resulted in a sharp edge which acted as a pre machined crack. We beleived that we had caught all these items but this one had escaped.
- The loads with the 140 grain SMK are probably at absolute maximum for the working pressure but I cannot verify this without testing. The very short ogive and long bearing surface will drive pressures. Regardless the gun should have operated without this problem as there should be a significant safety factor but the maching error removed this.
- The bolt was replaced with our current production unit. Since the inception of the Grendel I have made several small adjustments to the design to to add to the safety factors and aid inspection of the critical areas.
- The new carrier assembly is part of an ongoing project to upgrade the cyclic life and reliability of the upper reciever in adverse conditions and when subjected to very high round counts, in response to requests from some of our customers. The design is to increase the fatigue life of the unit not to allow for heavier than standard loads.
Bill Alexander "
"Does your mother know you're here?! Does she know you're staying the night?!" from FMJ