The gauge is the first thing you’ll notice on a box of shotshells, and it’s crucial to match this number with your shotgun.

In Britain, the standard 12-ga. cartridge is the 2 1⁄2", loaded with one or 1 1⁄16 ozs. of shot. With the resurgence of interest in side-by-sides, more and more British-made shotguns are coming to ...