Gun Terms and Abbreviations Glossary

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.

Abbreviations

• 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" bullet type in the modern day.

• HP - "Hollow Point". Refers to a bullet / projectile with a follow cavity at the tip, which is meant to expand to increase energy transfer in the target, increase soft tissue damage, decrease penetration, etc.

• 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.

• DMR - "Designated Marksman Rifle". These firearms fill the gap between a standard infantry rifle and a dedicated sniper rifle. Are often in a "full-power" rifle cartridge such as 7.62x51mm NATO, but not necessarily. They are typically equipped with longer-range scopes and are high-precision rifles optimized for accuracy and range. Often include heavy barrel and bipod, and are semi-auto with higher-capacity magazines than a dedicated sniper rifle in order to engage more targets more effectively at range. Often based on existing infantry rifles, but purpose-built for extended range. Examples include the Knights Armament SR-25 (7.62x51mm NATO), or the Mk 12 Special Purpose Rifle (5.56x45mm NATO).

• LMG - "Light Machine Gun". Typically much heavier than a typical infantry rifle and meant for suppressive fire. Often crew-served, at least for maximum effectiveness. Meant for suppressive fire, allowing the shooter to keep the enemy pinned down and allow for movement, flanking and so on. A major example would be the United States' M249 SAW.

• MMG - "Medium Machine Gun". A less-used abbreviation, but typically refers to guns similar to Light Machine Guns, but of higher caliber such as 7.62x51mm NATO. An example would be the M240 family used by the U.S. military. Simply put, "Heavier than a Light Machine Gun, but lighter than a Heavy Machine Gun."

• HMG - "Heavy Machine Gun". Typically refers to large automatic firearms firing large cartridges and mounted to vehicles such as tanks and other general-purpose vehicles like the United States' "Humvee" (HMMWV) and where weapon weight, recoil and so on can be an afterthought. An example would be the U.S. M2 and M2A1, which fire the large .50 BMG (12.7mm NATO) cartridge.

• GPMG - "General-Purpose Machine Gun". A less-used term overall, but appears to refer to "Medium Machine Gun" (MMG) type firearms such as the aforementioned M240 family. The concept appears to originate with the German MG 34 which was referred to as "Einheitsmaschinengewehr" (Universal machine gun). It was light enough to be carried by one man, while having high rate of fire and good firepower. It could serve the roles of light and medium machine guns, but even provide anti-aircraft and sniper support in certain uses.