My take......

I have a 625-9 in 45 Colt. It went back to S&W for rediculus end shake after around 1000 rounds. Some (50?) were Corbon 225gr & 1200 fps I think.

I also have a 460 XVR that also went back for gross endshake after a couple hundred rounds. Load shouldn't matter, right? It's a freaking 460 mag.

Both guns were repaired by stretching the yoke and resetting the barrel for a 0.006" B/C gap.

After 2000 or so 45 Colts (mostly std pressure with a few +P hadloads) the endshake in the 625 is still negligible as I recieved it back from S&W.

After a couple of hundred 460 mag rounds, the 460 XVR it also still as tight as when I got it back from S&W.

I think BOTH frames stretched from new and then stopped when they reached some critical stress. Perhaps the frames work hardened?