This morning I was shooting 2 rifles in 223 Rem. One is a Mini-14 and the other a bolt action. The brass ejected from the Mini-14 was hot and the BA was not? The ammo used was Black Hills factory 55 SP in both. Why would one be hot and the other not?

You were probably firing the semi-auto faster and therefore heating it up more than the bolt action?

simple - the brass was ejected from the auto before it got a chance to cool off in the chamber

I was actually firing them both at about the same rate. Also, the brass from the Mini-14 was still hot several seconds later when picked up off the ground; the brass from the BA was ejected onto the bench and picked up immediately.

quote:

Originally posted by butchloc:
simple - the brass was ejected from the auto before it got a chance to cool off in the chamber

Butchloc is correct here.....the key is "how long does the brass casing sit in contact with the cold chambert steel after firing. In the case of a semi auto the answer is not too long. In a bolt action the answer may well be over a second and that's long enough to cool the casing.

Ever have a .22 rimfire casing from a semi auto go down your collar?

OK, that makes sense. I have never had a .22 down my shirt, but lots of 9 MM, 40 S&W, and .45 ACP. I saw a girl get a nice red mark on her boobie when one caught in her bra.

Counterintuitive as it may seem, the brief time that a fired case is in contact with the chamber walls in a non-automatic action allows the case to transfer most of the heat from igition to the much greater mass of the steel of the barrel. Amazing how much difference this makes, isn't it?

This same phenomenon also keeps the barrel (chamber section at least) of an automatic rifle a bit cooler than it otherwise would be (some of the heat is ejected in the form of a hot case), but I doubt that this cooling effect is even measurable.