Green’s Dictionary of Slang

mag n.4

[abbr.]

1. [mid-18C+] a magazine.

2. [1940s+] a magazine of bullets.

3. [1950s+] magnesium; esp. with ref. to magnesium alloy tires.

4. [1970s+] (US) a magnum pistol.

5. see magazine n.

6. see magsman n. (1)