I just had my old-style, easy open frame returned from T/C. I accidently had my G2 and the older one disasembled and on the bench at the same time. Of course, I put the ML barrel on the wrong frame. It wouldn't close because of a pin sticking down from the barrel (it's put there so you wouldn't do such a thing). Something broke in the frame since it wouldn't cock or fire any more.
The bright side is that I now have a frame with all new interior parts, and thanks to T/C's fantastic warranty it only cost me the cost of shipping the frame to T/C. That's right, they fixed it and returned it at no charge! Thanks, T/C!
By the way, I have other 23" carbine barrels that fit on both frames interchangably. I don't know why, but T/C doesn't want you to put the ML barrels on old frames. It doesn't seem to have anything to do with pressure, but they have some reason I'm sure.