Went to the range yesterday to fireform some virgin brass for my .243. After ejecting them from the chamber I always inspect my fired cases and by doing this I obviously get to feel their temperature.

The first few cases came out warm, probably around 45-55 degrees C. The next one would come out significantly hotter, around 80 degrees C.

I'd fire a few more...same thing. I was waiting about 3 minutes between shots so the chamber/bbl stayed at a contant temp and was making sure the cartridges were sitting in the chamber about the same amount of time before being fired, then ejected straight after firing.

I also tried tapping the cases so the powder was laying in the same position for each shot but kept getting a couple of warm cases then a couple of hot cases. Even after letting the bbl cool down, next shot might produce a hot case. There was no pattern emerging as to why this was happening.

The pet load was an 80 grain projectile seated .012 off the lands (measured at the ogive) over 38.0 grains of ADI 2208 (Varget). Rem case and Win LR primmer. 3040 fps from the Rem 7600's 22 inch bbl.
None of the cases, warm or hot showed any pressure signs. No unusual muzzle blast or recoil. Groups were consistant.
I take a lot of care measuring my powder charges and case preparation. All the cases were put through a Lee Collet neck die before being checked for length and chamfered. All of the bullets took about the same amount of pressure to seat.
Any theories......

The temp differance is probibly based on how long they sat in the chamber after fireing. It doesn`t take long for the chamber to suck the heat out of a case. If you want to feel a hot one have a guy shoot a semi from the next bench and drop a empty or two down the back of your shirt. Trust me, they stay hot a long time..............

Ol'Joe
That was my first thought but all the cases where ejected straight after firing so they were only left in the chamber for a second or so. Just to prove it I left a few in the chamber longer than usual, again no pattern emerged. Some were left for 5 seconds and would be warm, others left for 1 second would be hot.

I'm inclined to think it might have something to do with some of the cases stretching more than others as virgin brass is no guarantee of uniformity. But I don't have enough experience to put this down to the cause.

I would guess, that the longer you leave it in the chamber, the more heat the barrel extracts from the case, never paid any attention to it tho... interesting.