Glossary of Gun Related Terms

Gun terms defined:

1. Automatic Loader (Autoloader) – A gun which, when the trigger is pulled and the chamber is loaded, will fire one round, eject the spent casing, and chamber a fresh round. Also referred to as Semiautomatic.
2. Barrel – The tube like structure down which the projectile(s) travel. Can be rifled or smooth bore.
3. Barrel Shroud – A safety feature whereby the barrel of a gun is enclosed in a perforated metal or plastic guard, preventing the user from being burned by a hot barrel. This safety feature was included in the 1994 “Assault Weapon” ban.
4. Cartridge – the self contained assembly of primer, gun powder, and projectile that is commonly used with modern firearms.
5. Caliber – A measure of the internal bore diameter of a gun’s barrel. Measured in inches or millimeters. E.g. .22, 9mm, .40, .45.
6. Clip – A device for charging (filling) a gun’s magazine, and an integral part of the gun. Most guns use Magazines rather than clips, so many people really mean Magazine when they say Clip.
7. Collapsible Stock – A feature of a gun whereby the stock can be lengthened or shortened to fit the user, or to allow the gun to be stored more easily (such as allowing storage in a smaller gun safe). This comfort and safety feature was included in the 1994 “Assault Weapon” ban.
8. Elevation – Vertical adjustment of a gun’s sights so that the projectile lands neither too high or too low.
9. Flash Suppressor – An feature which attaches to the muzzle of a gun’s barrel and helps prevent the user’s vision from being temporarily effected by the muzzle flash.
10. Folding Stock – A feature of a gun whereby the stock can be folded back to allow use of the gun in more confined places, or to allow the gun to be stored more easily (such as allowing storage in a smaller gun safe). This utility and safety feature was included in the 1994 “Assault Weapon” ban.
11. Full Metal Jacket (FMJ) – A bullet that is completely enclosed in a jacket of metal, often copper. The jacket protects the softer lead core of the bullet, allowing deeper penetration of the target. Full metal jacket bullets often have a more aerodynamic shape than hollow point bullets, and will feed more reliably in certain automatic loading and fully automatic firearms.
12. Fully Automatic (Machine gun) – A gun which, when the trigger is pulled and the chamber is loaded, will fire a round, eject the spent casing, and chamber a fresh round, and automatically repeat this process so long as the trigger is held down. Not to be confused with an Autoloader.
13. Gauge – A measure of the internal diameter of a shotgun’s bore. A few of the common gauges, in descending size are 10, 12, 20, with 12 gauge being the most common today.
14. Gun Powder – The substance which burns, rather than explodes, propelling the projectile.
15. Handgun – A smaller gun held with one or two hands. Generally a revolver or pistol.
16. Jacketed Hollow Point (JHP) – A bullet with a jacket (often copper) that surrounds the base and sides of the bullet, but not the front. The front of the bullet is made of lead with a hollow tip, which allows the bullet to flatten out and expand upon hitting its target. Such bullets are more effective on their intended target, and are less likely to over penetrate and strike an innocent bystander.
17. Magazine – An ammunition feeding device. Not to be confused with a Clip. Most guns have a magazine rather than a clip.
18. Muzzle – The end of a gun’s barrel from which the projectile(s) emerge.
19. Muzzle Brake – A device which attaches to the muzzle of a gun in order to redirect some of the escaping gases back toward the user. This reduces recoil but increases the noise heard by the user.
20. Muzzle Compensator – A device which attaches to the muzzle of a gun in order to redirect some of the escaping gases upwards. This reduces the tendency of the gun’s muzzle to rise upwards (and can also reduce recoil somewhat) when the gun is fired, allowing the user to stay on target. This utility and safety feature was included in the 1994 “Assault Weapon” ban.
21. Out of Battery – A condition whereby a gun’s action is not all the way closed.  A gun that is fired while out of battery can fail in a catastrophic way, causing destruction and injury.  Many modern firearms include safety features to prevent discharge while out of battery.
22. Over Penetrate – The tendency of bullets to pass through their intended target and strike a person or object downrange of the intended target. The use of hollow point bullets and shot from a shotgun can reduce but not eliminate this risk.
23. Pistol – A semiautomatic hand gun which (generally) stores ammunition in a magazine. Not to be confused with a revolver.
24. Pistol Grip – A grip similar in appearance and function to the grip of a pistol, which protrudes below the action of a gun. This is a safety and utility feature of a gun, often a rifle or shotgun, allows the gun to be securely gripped by the user. It also helps the user to manage the recoil. This utility and safety feature was included in the 1994 “Assault Weapon” ban.
25. Primer – The small amount of explosive in a cartridge which causes the gun powder to burn, after being struck by the firing pin.
26. Pump Action – A common action type for shotguns, but also available on some rifles. The user slides the forend of the gun to the rear in order to eject the spent shell/cartridge, and then to the front to chamber a fresh shell/cartridge. A very reliable action type, as it is not dependent upon the previous shell/cartridge firing in order to fire the next shell/cartridge.
27. Recoil – The tendency of the gun to move backwards as the projectile goes forward. Recoil can be mild enough that it is barely noticed, or sever enough to cause injury if the gun is not held properly. Recoil will depend primarily upon the weight of the projectile, speed of the projectile, and weight of the gun,
28. Revolver – A handgun with a revolving cylinder, which holds the cartridges. Each time the trigger is pulled, the cylinder rotates and allows a fresh cartridge to be fired. Revolvers are more reliable than a pistol since it is not dependent upon the previous cartridge firing in order to fire the next cartridge.
29. Rifle – A shoulder fired gun designed for longer ranged accuracy. Generally rifles shoot bullets that are more powerful and longer ranged than handguns, at much higher speeds.
30. Rifled – The cutting of spiral grooves into the interior surface of a gun in order to cause the bullet to spin. This greatly improves accuracy and is common on modern handguns and rifles, and even on shotguns specially designed to shoot slugs.
31. Safety – The mechanical device(s) which are designed to prevent the gun from firing accidentally. Safeties, while good, are no substitute for using the utmost care around guns.
32. Semi automatic – See Automatic loading.
33. Shell – A self contained shotgun cartridge. Can contain Shot or Slugs.
34. Shot – Spherical balls of lead, steel, or another metal which are fired from a shotgun. 00 Buckshot, the size of shot recommended for home defense, will have 9 .33 caliber (1/3 of an inch diameter) pellets in a stander 2.75″ 12 gauge shell.
35. Shotgun – A gun which fires multiple pellets (called Shot) at once with each pull of the trigger. Shotguns can also be used to fire Slugs.
36. Slug – A large bullet fired from a shotgun. Slugs used to be crude, large diameter pieces of lead which were fired from smooth bore shotguns, but modern slugs can match the performance of some big bore rifles.
37. Sound Suppressor – A feature which attaches to the muzzle of a gun’s barrel and reduces the amount of noise emitted when the gun is fired. A feature which can make the gun less hazardous to fire around people without hearing protection. This utility and safety feature was included in the 1994 “Assault Weapon” ban.
38. Smooth Bore – A gun whose bore is not rifled, as is the case with many shotguns as well as older muskets.
39. Stock – The part of a rifle or shotgun which is braced against the user’s shoulder when firing the gun. Allows for accurate aiming and helps the user manage the recoil.
40. Wadcutter – A bullet designed for target practice, with a flat frontal surface which produces smooth round holes in paper targets, allowing for easier scoring.
41. Windage – Horizontal adjustment of a gun’s sights so that the projectile lands neither too far to the left or the right.

Note: Terminology is both contingent and contestable. That means that on finer points (such as what constitutes a “pistol” or “cartridge”, or what separates a “muzzle brake” from a “muzzle compensator”), reasonable minds may differ.  Some terms also vary be geography. The above definitions represent what this author believes to be the majority view on such contested points.