It is a relatively difficult thing to make a semi-auto function reliably with a rimmed cartridge like the .38 Special.
Coonan has found a way to make it work.
He has a patented system on his magazines (they're $60 bucks each!) with a rotating follower. It prevents the rims from stacking too hard on top of each other. As you can see here, the piece in the middle allows the follower to rotate. Image: http://cdn2.armslist.com/sites/armslist/uploads/posts/2012/03/25/347660_01_coonan_model_b_357_640.jpg
Check out this guy's channel if you have doubts. He has a bunch of high speed video of it and it looks pretty sweet. Also in this video, he has a guy shoot it for the first time and he loves it. http://www.youtube.com/watch?v=bfLLyBruZbk
Something to add is that you get even more velocity out of the .357 magnum round in a semi auto since there is no cylinder gap. I forget the exact amount but I think it's somewhere around a 25% velocity increase.
I've done a lot of homework on this handgun. It's not child's play. It's a very well-thought out design and I can't wait to have money so I can own one.
This gun WILL BE my my next 1911.
This post was edited on 12/6 at 12:15 pm