Originally Posted by Absalom

If there is an emergency and +P is all you've got, go ahead, it will not blow up, but otherwise indeed avoid any hot loads.

S&W revolvers do have a safety feature, but it failed in 1944 and killed a sailor, leading to the development of an improved one which yours doesn't have. In normal use, any risk is remote.

Yes, it most likely went to Britain, although other allied countries like Canada are possibilities too. Any surviving markings might or might not provide clues. If you post the serial number from the butt, someone here will give you a decent guess when it shipped from the factory. And it is too early to be a pre-Model 10; those didn't start until 1948 (although this gun does indeed belong in the eventual Model 10's family tree).