Yes as I recall Buck had opened the chambers to 3" & was firing massive loads of Blue Dot with very heavy shot charges when the gun started opening. He had started with the heaviest loads listed for the 3" magnum in the manuals & worked "UP" from there. I can't recall that I have ever heard of this being a problem with Smith guns using regular, even max, loads. It has been a problem with some NID's. As I recall it was a poor condition hammer gun with pitted barrels, yet he never "Blew" anything, just started opening it so quit at that point.
I do not know if he had the gun mounted un-movable for these tests or not. If not it may well have been the recoil motion being sharp enough that the "Barrel Dip" in recoil was putting enough force on the bolt to cam it around. Anyway you cut it thogh this gun was taking far heavier loads than it was designed to handle.
