You were running a max load of a fast burning powder. At that level of performance, any number of things could cause or contribute to the issue:
1) The brass was previously used in a Glock, already with a weak spot near the base.
2) Brass length after several uses at max pressures cause the headspace to increase to the point where there was a very small area of brass unsupported in the 1911, but the gun still went into battery and fired the round.
3) Brass worn enough that it wasn't up to handling a max load.
4) Bullets not crimped tightly enough, causing them to set back during recoil while in the magazine. If this happens with a max load of fast powder, it can drive pressure through the roof. Do you recall if this happened on the first shot of a magazine? Last shot? Somewhere in between? If it happened later in the magazine, bullet setback is more likely. Also, in a tapered crimp cartridge like 45acp, jacketed will set back more readily than unjacketed lead bullets, because brass squeezed against copper produces less friction than brass squeezed against copper.
If they were my reloads, my corrections would be:
1) Inspect all the brass: Get rid of bulged or obviously worn cases. Measure case length and trim if needed.
2) Increase the crimp.
3) Stick with decreased powder loads, particularly for plinking rounds. People have a tendency to want max loads, but it doesn't serve much purpose in target shooting ammo. Harder on all of the gear, not likely to be more accurate than a softer load.
1) The brass was previously used in a Glock, already with a weak spot near the base.
2) Brass length after several uses at max pressures cause the headspace to increase to the point where there was a very small area of brass unsupported in the 1911, but the gun still went into battery and fired the round.
3) Brass worn enough that it wasn't up to handling a max load.
4) Bullets not crimped tightly enough, causing them to set back during recoil while in the magazine. If this happens with a max load of fast powder, it can drive pressure through the roof. Do you recall if this happened on the first shot of a magazine? Last shot? Somewhere in between? If it happened later in the magazine, bullet setback is more likely. Also, in a tapered crimp cartridge like 45acp, jacketed will set back more readily than unjacketed lead bullets, because brass squeezed against copper produces less friction than brass squeezed against copper.
If they were my reloads, my corrections would be:
1) Inspect all the brass: Get rid of bulged or obviously worn cases. Measure case length and trim if needed.
2) Increase the crimp.
3) Stick with decreased powder loads, particularly for plinking rounds. People have a tendency to want max loads, but it doesn't serve much purpose in target shooting ammo. Harder on all of the gear, not likely to be more accurate than a softer load.