A lot of things can happen to brass when it's fired, these are a few.   I don't worry much about split necks (the brass gets sent to the recycler), but a case head separation or rupturing is very, very bad.

A .45 ACP case rupture, no signs of over pressure with 5.2 gn. of Bullseye, behind a 185 gn. bullet, and a CCI 300 primer.   This may have been caused by reloading a case previously fired in a Glock, thats the only explanation I can readily see.

Notice the head stamp is CBC, Magtech, apparantly made in Brasil.   Note: The edges of the primer are still round, and there is no crater around the firing pin strike.   Also the blown out part is just about the same as the area unsupported by a Glock.

Again, a good look at the case head, round primer edges, no crater around the firing pin strike.   Mfgr's stamp: CBC (Magtech).

Another close up.   Again: no signs of over pressure, the edges of the primer are still round, and there is no crater around the firing pin strike.

A different angle.

A .45 ACP and 357SIG each split.   These are usually caused by a gunch or nick on the lip of the case mouth during the last reloading.

The split .45 ACP on it's side.

The split 357SIG on it's side, showing the split.