Originally Posted by Ed Zachary
I believe it is because you have controlled the muzzle flip.
I noticed with mine that if I get a bit sloppy with the grip and I let the muzzle flip way up I get the casing between the eyes.
If I control the muzzle flip, the spents go off to the right like they're supposed to.
That was my main theory as well. Since I only have the two Defender mags, I've used some standard 1911 mags when I've taken it to the range. I haven't noticed which mags were in it when it happened, but since it's so infrequent, I really think you're right about the flip.