Bolt thrust force with the Grendel compared to 223

[Fess]

I know this thread is largely academic. When talking about bolt thrust some people talk about the strength of the brass. In my opinion you should not rely on the brass to reduce bolt thrust when estimating safety factors. Consider the situation of a case head separation: the force on the back of the case is going straight into the bolt, and the shape and length or surface finish or friction of the chamber or barrel has nothing to do with it. Pressure is force per area, and the area in question is the cross section of the back end of the chamber.
2¢

As you noted, it is best to plan for the worst-case scenario even though brass usually expands enough to grip the sides of the chamber and reduce the thrust seen by the bolt. I know that in the Lee Enfield days, British proof testing of each rifle involved oiling the cartridge to minimize "case grip" and maximize bolt thrust.