Yeah, but the cases are about 1/8" longer. They are called 10mm's. Seriously, Bomar made a .40 cal barrel to retrofit to the 10 mm frame/slide. If you can find one, that's about the only way to have a single stack .40. I guess you could have your 10 mm barrel bushed and recut for .40, but the bullet wuold have a jump to make to the rifling. Maybe no worse than a revolver. Seems like there was a post here a while back where someone did that.