I have a Safari Arms .40 CB barrel I fitted to a Colt 1991A1.
It does work okay - but a couple of caveats:
1. Make sure you have the ammo with small primer pockets, or else you can expect blown primers. Cor-Bon has some useful notes on their website.
2. If you reload, make damn sure your bullets have a tight fit in the case mouth, and a tight crimp. A bullet with a chanellure, crimped in the chanellure, is a good additional precaution. Because of the bottle neck case design, the bullet can very easily get pushed deeper in the case while feeding, which can cause a scary pressure rise.
I also have a 10mm Colt, which I prefer to the fullpower CB, if for no other reason than you get two more rounds in the mag.
One thing I have not heard anyone mention is that, you can drop in a .400 CB barrel into a .45 ACP, load it down with 135 gr subsonic loads, and have a very mild shooting 1911, for less than the cost of a .22 conversion, and way less than the cost of a 9mm 1911, or even a .38 special revo. Mine runs just fine with these light loads.