Headspace (firearms) - Wikipedia

Cartridge (firearms) - Wikipedia

Why was the rifle round named, '7.62 x 54mmR' by Russians when the 'R' represents the English term, 'rimmed?' - Quora

What is headspacing, and why can't I do it instead of a certified gunsmith? - Quora

9.3X57 headspace question

Do Centauro 2 and M60A3 Leonardo, which have the same cannon 120/45, use the same rounds? - Quora

Headspace, Gun Wiki

Blowback (firearms) - Wikiwand

Do Centauro 2 and M60A3 Leonardo, which have the same cannon 120/45, use the same rounds? - Quora

Can you use a .45 auto rim in .45 Colt revolvers or single-shot rifles, as well as in .45 ACP revolvers? - Quora