I had a partial case head separation using a 1.8oz buffer

[grayfox]

DN I am coming to the same conclusion, about the unsupported brass, particularly with a Lapua/Odin combination setup. But to your post, I believe near to the base, the heat/temperature may be higher early in the ignition process but pressure, probably not. Pressure increase won't really occur until the entire volume of the case/bullet interior has that pressure increase. That might be some microseconds after the heat towards the base increases. But that heat can still have an impact on the brass down there, which will accelerate as the pressure (and deflagration) proceeds. Pressure buildup needs to have some gas generation, and pretty much the entire volume will see that pressure. Any local pressure beginnings in that ignition wave, will propagate forward, not build up in place down at the base.