I've fired .32 ACP in a .32 S&W Long revolver with decent results and no problems.



"It should be noted that there is more difference in case diameter between the .32 Long Colt and .32 S&W Long than there is between .32 S&W Long and .32-20..."


Case mouth perhaps, but the .32-20 is notably different otherwise, being a tapered case with a neck.

I once read years ago that a .32 S&W Long could be fired in a .32-20 revolver in a pinch so tried that combination. They would fire but made ugly misshaped cases with occasional splits.

Here's a .32 S&W Long flanked by a .32 Short Colt and a .32 Long Colt.



I have a Colt New Pocket in .32 Long Colt. When I got home from the gun show with it I figured on firing ammo from supplies of .32 S&W Long in it but was wrong about that. The .32 S&W Long is just a hair's breath larger in diameter and won't chamber.

The .32 Short and Long Colt ammunition gives a decent performance in a .32 S&W Long chambered revolver.