Bolt thrust force with the Grendel compared to 223

[LRRPF52]

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. If you try to hold your thumb over the end of a garden hose, the length or volume of the hose has nothing to do with it--only the pressure and size of the opening. Again, the size of the bolt face is not the area to worry about. A rebated rim case like a 284 can put more load on a bolt than a 308 at the same pressure. If you consider similar materials and pressures, then it's just a matter of the area you're trying to hold pressure in. If a case has twice the cross-sectional area (measure the widest part of a fired case), you can expect twice the bolt load.

To answer your question, it is probably safe to do if you are reasonable in your approach. Most factory actions have a significant safety factor. For example, a remington 700 designed around a 30-06 can be had from the factory chambered in 338 lapua. So one easy check is whether the same action is offered in larger chamberings from the factory. An example of this is the howa mini, which is offered from the factory in 223 and ppc bolts.

2¢

Definitely don't rely on brass for pressure containment, as it is extremely soft and bendable by hand. The brass instantly becomes plastic with the pressures generated within the chamber.

If you study the history of cartridges, brass was the next evolution from paper cartridges, which means they were looking for a more durable container that could store and feed better than the paper cases. It's main purpose is to contain the propellant, hold the projectile in place, and have a seat for the primer before and during chambering.