What caused the damage to this case? 45ACP

[noylj]

The initial blow-out for the bottom case was at the extractor groove. This area is ALWAYS exposed, so it wasn't an unsupported chamber, as that area is always unsupported. Also, a proper .45 load simply doesn't have the pressure to blow out like that and certainly NOT to set off the next round.
Was the case head expanded on the fired case? That is a sure sign of over-pressure.
That kind of blow-up is almost always due to over-pressure (accidentally used the wrong powder or the wrong powder charge) and less likely to be a bad case. Not sure what caused the next case to blow, as the escaping gasses had to be very hot.
The one time I had a case rupture (.40S&W), it broke the extractor and blew out the bottom of the magazine, but the top round in the magazine showed not particular issue other than some surface soot.

[Dan_69GTX]

Thanks for the info!

Hope this never happens to me!

[firecracker6]

It seems to me that it would have to be a double charge.  I've never had a problem with 231 in a powder measure so inattention was the likely cause of the problem.  Having said that, I try to pay very close attention to what my powder measure is doing.  I've had hoppers get clogged, rotors get stuck, static electricity throw off my charge weights and probably a few other things I've forgotten about.  The results have been everything from excessive charge weights to no charge at all.  When I load on a single stage, I try to remember to shine a light into all the cases in the load block and check them before I seat the bullets.  In my experience, the wife and kids talking to me at the same time I'm trying to reload is highly detrimental to the reloading process.