I heard the odd noise -- it was like a wet firecracker -- and immediately stopped firing to investigate. Wound up tapping the bullet out of the barrel with a cleaning rod and a rawhide hammer I happened to have in my kit.
Have never had that happen with my 1911A1, so I don't know if it would cycle the larger and heavier round. The .38 Super rounds are extremely hot (flowed primers are commonplace with standard loads) so maybe that extra oomph is what cycled it.