Gun Terms and Abbreviations Glossary

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In the world of guns, you'll find many gun-related terms and abbreviations. Some are still in common use, some are antiquated, and many are somewhere in-between. We've laid out a vast number of these terms as to hopefully clear up any confusion.


  • AA - "Anti-aircraft". Refers to anti-aircraft guns, which typically have high rates of fire, multiple barrels and fire extremely powerful cartridges such as 20x102mm, 20x138mmB or various others.
  • AP - "Armor-piercing". Typically refers to ammunition or projectiles with features such as a tungsten core (or hardened steel, etc). Early on, the term usually refered to being able to penetrate steel armor and the like, though in the modern day, their use is more geared toward better penetration through concrete, ballistic glass, body armor and so on. Note that handgun projectiles with steel cores that are intended to pierce soft body armor are typically considered "armor piercing", but not necessarily in the classical sense of the term.
  • API - "Armor-piercing incendiary". Penetrator core, typically tungsten, with a small high explosive charge at the tip that explodes upon impact, and typically contains some amount of other incendiary material eg Zirconium Powder for various purposes such as causing fires that are not easily extinguished.
  • FMJ - "Full metal jacket". A "jacket", typically copper, that surrounds the inner lead projectile. Helps with penetration, slowing down expansion of the softer lead bullet. The standard in the modern day.
  • TMJ - "Total metal jacket". Largely the same as FMJ bullets, but the entire bullet is jacketed (including the base), which is not the case with FMJ ammo, hence the distinction. Has the major benefit of reducing lead exposure.
  • TC - "Truncated Cone". You'll very rarely see this abbreviation. It's basically only used by Remington for some of their .22Lr ammunition, such as their "Yellow Jacket" and "Viper" loadings. Refers to the unique shape of the projectile as compared to typical round nose and the like.