Hello Vincent! This round is the same as 7.92 x 57, 7.92x57mm Mauser, 8x57mm, 8 x 57 JS, or 8 x 57 IS. I'm nearly certain it is the correct ammo for your 1940s Mauser. Just make sure your rifle isn't chambered for a rimmed variant such as 8x57mm JRS or 8x57mm JR!