[sourceless]

This is, unfortunately, a misconception.

Sure, a bullet the same size or smaller will 'fit' in a given barrel, but a depending on its weight and dimensions it will, at best perform equally, and at worst destroy the barrel.

But a bullet isn't the whole story; the rest of the cartridge has to fit snugly for the action of the gun to lock properly. Again, best case - the gun doesn't fire. Worst case, the action blows up.

This is a pretty simplified overview, but unfortunately the assertion above is a (pretty absurd) myth. Sorry :(

[more_corn]

It’s technically possible though. The case of 38sp -> 357mag is a working example. The cartridge is longer and pressures higher so you don’t want to load a 357 into a 38 (and often can’t). But you can run 38sp in your 357 all day long.

One warning I received from my gunsmith though is that you’ll want to clean the barrel super well when switching so the powder ring of the longer round doesn’t cause problems. Hasn’t blown up in my face yet. Will report back if that changes.