I have seen many modern barrels that have been sent to Charlie Boswell that have been split, not just ring bulged, at the choke. Owners have requested that he cut off the damaged end of the barrel and re-thread for tubes. None of them were caused by steel shot. All were caused by Hevi-Shot, by owners' admission.
Charlie warrants his two lines of choke tubes, Comp-N-Chokes and Kick's High Flyers, with anything but Hevi-Shot. The point is that the same thing happens with steel in chokes that happens with Hevi-Shot........... bridging, leading to split chokes.
That said, Worth Mathewson wrote in his book BIG DECEMBER CANVASBACKS that he shot a tightly full choked L.C Smith for years with steel shot before taking it to a gunsmith for some other problem and finding that it was choked so tightly. He said the barrels never exhibited any problem.
I don't use it in my vintage doubles, but my BSS gets a regular diet of it every year during duck season. I won't worry Browning with it if I ever have a problem.
SRH
