The N-frame cylinder was designed for the .44 Special, and Elmer Keith broke some cylinders in .45 Colt when trying for hot loads.

Frankly, I think the .45 N-frames are marginal with anything other than factory ammo pesssures. New steels and heat treatments on modern ones are better, but still, if you want hot ammo, get a .44 Magnum.

I think this is one reason why S&W was reluctant to offer many .45 guns, not just because they didn't want the Colt name on their barrels.

Keith went to the .44 Special for hot loads because the chambers were thicker at that critical place. I'm not guessing about that. He told me so, and I think mentioned it in his writing.