After looking at the OP's blown casing again and the pics of the 9 and .40 barrels side by side with a round, I don't think the primer was struck prior to going into battery. The location of where the casing peeled back could have just as easily have happened to either of the barrels I have shown. The round in the .40 would have peeled forward but just not as far. My conclusion is that the casing was defective and the malfunction would have occurred regardless of how far the round was seated in the chamber of the barrel.

That's my two cents and I'm sticking to it.