Can you be a little more specific about the occurence? I've never seen anything of the kind with a Glock. Both myself and my brother own Glocks in .40 and 9mm and have yet to see anything but flawless action with ours and anybody shooting Glocks(well, aside from a limp wrister or two).
The ramp on a glock is a bit more opened up than on a normal semiauto, this assists in jam free operation.
However removing the extra material at the mouth of the chamber
leaves some of the bullet casing unsuported by the chamber.
This is ok for factory loads but may result in the unsupported section of the bullrt case "blowing out" or rupturing when using hot handloaded ammo.
I am uncertain if P+ ammo would result in the same situation.
The glocks a fine weapon but is susceptable to this condition. Ive seen it happen