I'm pretty sure the hole was the "improvement" as when I first learned that tidbit I remember thinking, "You're kidding?"
This site seems to agree with that.
I played with one or the other some years back but I can't remember for the life of me which one it was. It was the first time I fired a full auto weapon. I was dissapointed, I had expected it to be a lot more fun than it was...
(Flintlocks, Barret Light 50's, cannons chambered for beer cans filled with cement... those things are all as fun as you would imagine. Full auto, that got boring in a hurry.)
But, Brady didn't seem to be too picky about it.