So let's get started...in no particular order
Hoplophobe: A person with an unreasonable fear of weapons. This follows the tradition of naming phobias using the Greek word for the item. Hoplon is the Greek word for weapon. So someone who fears an inanimate object that is or can be a weapon, they are a Hoplophobe. The name of the phobia was introduced by Col. Jeff Cooper.
Gas Check: A small cap of copper that covers the bottom of a lead bullet. The purpose is to seal the barrel so that gas cannot escape around the lead bullet when using high pressure loads.
BATFE: Acronym for Bureau of Alcohol, Tobacco, Firearms and Explosives. Originally part of the Dept of Revenue (taxes on alcohol & tabacco) they enforce all Federal Gun Laws.
Breech: The area in which the cartridge or shell is inserted.
Chamber: The place in which the cartridge resides during firing.
Muzzle: The end of the barrel in which the bullet exists the gun
Carbine: A rifle with a barrel length of 20 inches or less, originally designed for Calvary (horse mounted troops), they were employed for paratroopers and are often used for hunting in thick woods or brush.
A.O.W.: Acronym for "Any Other Weapon", as defined in the National Firearms Act of 1934. No one really knows the correct definition, it appears to be anything BATFE says it is.
Magazine: a place to store ammunition or gun powder, also used to describe a removable, self contained clip that holds ammunition for the bolt. All repeating guns have a magazine: tube, box or removable.
Clip: used to insert cartridges into a magazine. Some clips stay with the gun and are ejected with the last round.
S.B.S. or SxS: this usually is an acronym for "Side by Side" as in a Side by Side or double barrel Shotgun.
Rabbit Ears: This is a term used to describe a double barrel (or SxS) shotgun that has dual exposed hammers. See the picture above.
M9: This is the military designation for the Beretta model 92, provided under contract to the U.S. Military. The guns are pretty much identical to the ones available for civilian purchase.
Gun show Loophole: No such thing exists. In the mind of a Hoplophobe, anyone who buys a gun without filling out paperwork with a licensed dealer is somehow "slipping through the cracks". Private sales between individuals has always been legal. in addition selling a gun to a person who is not allowed by law to posses one is against the law.
Hammer Bite/Slide Bite: This when the slide of a semi-automatic handgun cuts into the thumb and or top portion of the web of the shooters hand. Also when the hammer comes back and pinches the skin between the hammer and the frame of the gun.
Beavertail: An extension added to the grip or grip safety of a pistol to prevent the hammer and or slide from making contact with the shooters hand (see above).
B.U.I.S.: An acronym for Back Up Iron Sights, referring to metal sights that can be folded down when using an optic.
Chain Fire: This is when the firing of one cylinder ignites the powder in another cylinder. This was a risk in shooting cap & ball revolvers. Shooters of the day would seal the chambers in grease or wax to prevent a chain fire and also to keep the powder dry.
Chain Gun: A gun that uses external source of power to operate the mechanism. Usually referring to a machine gun that uses a bicycle chain to connect the action to the source of power. The term "Chain Gun" is a registered trademark of Alliant Tech Systems Inc.
L.O.P: This is short for "Length of Pull", this is the distance from the butt stock to the trigger, this is often adjusted for smaller stature shooters.
AR500: AR in AR 500 stands for "Abrasion Resistant", the steel is often used for targets dues to its ability to withstand glancing hits from bullets. It has no relation to the AR rifle.
Squib: This is a bullet that leaves the cartridge, but fails to exit the barrel. An Extremely dangerous condition that all gun owners should be aware of.
Suppressor/Silencer: A device attached to the muzzle end of a firearm to quiet the report generated by the explosion inside the chamber. There are many gun "experts" that will tell you that "silencer" is not the proper nomenclature, however, when Hiram Percy Maxim, patented the device in 1909, he used the term "silencer", so while a "silencer" does not completely silence a firearm, either term is appropriate.
Dry Fire: The act of operating a gun without live ammunition, sometimes artificial ammunition is used called "snap caps" which have a spring to absorb the firing pin inertia.
Snap Caps: A simulated cartridge with a spring loaded primer. Used for test firing or dry-firing a gun. Especially important with older guns whose firing pins were brittle and could break if dry-fired.
M.O.A.: an acronym for "Minute of Angle" or "Minute of Arc". This is a unit of measurement that is equal to 1/60th of a degree, measured as 1" at 100 yards, 2" at 200 yards, 3" at 300 yards etc.. Visit the NSSF website for more details:
Gunman: You hear on the news all the time that the "gunman" was "armed" with an AK-47. According to Jeff Cooper, you are no more a gunman (or "armed") because you have a gun that you are a musician because you have a guitar. Having a gun and knowing how to use a gun effectively are two different things.
Dragoon: Originally a term used to describe light infantry, that were often mounted on or transported by horse. When Samuel Colt built a special revolver for the U.S. Mounted Rifle Companies (Dragoons) the name became synonymous with the large heavy barreled revolver. A unique feature of the revolver was the squared back trigger, now known as the "dragoon trigger guard".
Pinned and Recessed: You will hear these words used to describe older Smith & Wesson revolvers (made prior to 1982). The earlier guns had screwed in barrels that were pinned in place, also the cylinders had recessed chambers where the cartridge rims would fit flush to the end of the cylinder. S&W quit making guns this way, not because they found a better way, but because they found a cheaper way. These guns are considered to be worth more money than the later guns.
Gas Operated Gun: This means that the automatic operation of the gun is propelled by gas that is scavenged from the barrel, and used to push a piston with a rod or a piston on the bolt (as in a direct impingement system on an AR-15 Rifle)
Recoil Operated Gun: This means that the automatic operation of the gun is propelled by the recoil. A recoil operated gun will have some sort of locking lug that holds the bolt against the breach until released by the recoil.
Blowback Operated Gun: Similar to the recoil operation, except that spring pressure is the only thing holding the bolt against breach. These guns tend to have larger and heavier bolts.
Cosmoline: A type of grease used to prevent rust & moisture damage to military weapons when put into long term storage.
Glass Bedding: This is a way of treating a rifle stock's barrel channel with fiberglass epoxy resin. The end result is a sealed stock that will not swell or shrink during changes in temperature or humidity which can affect the accuracy of a rifle by putting pressure on the barrel.
Hammer Spur: The ledge on the rear of a hammer that allows a thumb or finger to pull it back
Idiot Scratch: This is a mark commonly found on the left side (with muzzle facing away from you) of a 1911 pistol. The scratch is made by improperly swinging the slide release lever (which also acts as the barrel pivot pin) into place by dragging it across the frame. The proper installation involves pushing the pin straight in from the side.
Jungle Clamp: This is when a person clamps two magazines together, usually inverted from one another and held together with duct tape, but sometimes a special clamp is used. Read more here
Point Blank: This is a term derived from the french word for white (Blanc). While point blank originally meant the white part of the target, it now means the range at which a marksmen can hit a target without adjusting his sights for bullet drop. This is of course different for every gun and cartridge and although it could be correct, it does not necessarily mean "close range", point blank range could be as far as 200 yards away.
Scope dimensions: Telescopic sights for guns are measured using two measurements, the first ones are the power of magnification. For instance a 4X scope is magnified 4 times a person's regular vision. Adjustable scopes will have the two numbers separated by a dash, for instance a 3-9X scope is adjustable from 3X power to 9x power magnification. The second number is the objective lens diameter, measured in millimeters. The objective lens is the one at the muzzle end of the scope, the larger the diameter the more light it can gather. A scope designed for low-light conditions will have a larger objective lens diameter.
So a scope with 3-9 adjustable magnification with a 42MM objective lens will carry a designation of 3-9x42mm.
Eye Relief: Also a term used with scopes. This is the distance the eye needs to be from the scope to get a clear sight picture. Rifle scopes had a short eye relief, whereas pistol scopes have a longer eye relief.
Mil-Dot: These are the range finding dots located on the reticule of a scope, it allows the shooter to estimate bullet drop or windage and how far off center the shooter should aim the gun
Dope Bag: This is an old term derived from the shooter "doping the wind" which is to discover the direction and speed the wind is moving in order to adjust their aim. It came to mean a bag for holding ammunition or shooting tools.
Blunderbuss: An old muzzle loading shotgun that had a belled muzzle, it was loaded with a variety of things including nails, glass, rocks and lead balls. They were used by sailors to repel pirates.
Single Action: A revolver or semi-auto pistol in which the trigger's sole job is to release the hammer, allowing it to strike the primer (the hammer must be manually cocked before pulling the trigger)
Double Action: In a double action gun, the trigger both cocks and releases the hammer, most double action guns will have a hammer spur, allowing the user to fire the gun in single action (by cocking the hammer manually) and double action. Single action trigger pulls are always lighter as they do not have to overcome the resistance of the hammer spring.
D.A.O.: Double Action Only, a gun whose hammer spur and or single action sear has been removed making the trigger pull double action only.
L.P.K.: This is an acronym for "Lower Parts Kit". This is usually in reference to the parts for a lower assembly of an AR-15 Rifle.
BCG: This is an acronym for "Bolt Carrier Group". This is usually in reference to the parts for a bolt assembly of an AR-15 Rifle.
Buffer Tube: This is the tube that makes up the shoulder stock of an AR-15 Rifle, the buffer & main recoil spring reside in the buffer tube.
Flat Shooting: When someone describes a cartridge, bullet or chambering as "flat shooting" what they are saying is that the particular cartridge moves at a very fast speed for its weight and the amount of bullet drop over the normal range is minimal.
B.A.R.: An acronym for Browning Automatic Rifle, the first B.A.R. was the U.S. Military M1918 (see below). The name has since been used by the Browning Company as a designation for all their auto-loading rifles.
Forcing Cone: The flared breech end of a revolver's barrel, this is the entry point for the bullet after it jumps the gap between the barrel and cylinder
P.P.C.: Acronym for Police Pistol Competition
IPSC: Acronym for International Practical Shooting Confederation
I.D.P.A.: Acronym for International Defensive Pistol Association.
Rimfire: A cartridge case with no primer, the priming agent is built into the rim.
Centerfire: a cartridge case with a removable primer, that ignites the powder
O.D.: sometimes expressed as OD Green, the OD stands for "Olive Drab" the matte green color used by the U.S. Military for most of the 20th century
F.D.E.: Acronym for the color, "Flat Dark Earth", a medium dirt color.
Lug: This could be used to describe the material under the barrel of a gun (usually revolvers), the cross bolt that absorbs the recoil or a spot at which to mount a bayonet or accessory.
Bandoleer or Bandolier: A belt or sling that contains pouches for storing ammunition, it is a way to distribute ammo quickly among troops during battle.
Bore Snake: A device used for cleaning the chamber and bore of a gun, the cloth "snake" has embedded brass brushes to help clean the fouling left behind from the bullet and powder residue.
Choke: just as you might guess this is a restriction at the end of the bore of a shotgun barrel, it changes the characteristics of the shotgun pellets as they leave the muzzle. There are 4 types: Full Choke, Modified Choke, Improved Cylinder and Cylinder Bore (which is no restriction at all).
Muzzle Brake: A device mounted on the muzzle to direct the muzzle blast in a different direction to aid in recoil management. Also called a recoil Compensator.
Flash Suppressor: Also called a flash hider, a device mounted to the muzzle of a firearm to cool the gases and reduce the flash signature. This is to prevent the shooter from being blinded by the flash of light and may also help hide his position (although this is a minor benefit from most flash suppressors).
Headspace: The distance between the bolt face and the "step" in the chamber that stops the cartridge's forward progress. The step could interface with the cartridge rim or the shoulder on a rifle cartridge.
High Brass/Low Brass: This is used to describe a shotgun shell. Higher pressure shells use more brass at the base, lower pressure ones use less.
Bullpup: A type of stock for a rifle or shotgun that moves the action/receiver assembly to the shoulder stock area, making the gun's overall length much shorter (see below).
Gauge: Used to describe the size of a bore of a shotgun, it is measured by how many lead balls, sized to fit the bore it takes to make 1 pound. So a 12 gauge shotgun round slug, is 1/12th of a pound in weight.
Buntline Special: A long barreled Colt Single Action Army Revolver. An old legend told of Ned Buntline, an author of dime novels, ordering some of the guns from Colt and gave them to the objects of his novels like Wyatt Earp & Bat Masterson.
Extractor: a clamp that secures the rim of the cartridge case to the bolt face.
Ejector: a post or spear that pushes against the opposite side of the case from the extractor, when the bolt is moved backwards the cartridge hits the ejector and kicks the case out of the ejection port.
V.F.G.: Acronym for Vertical Fore Grip, added to rifles & carbines, when added to a pistol it becomes an A.O.W..
Rimless: This is actually a misnomer, referring to the rim on a cartridge case, a rimless case still has a rim, but the diameter is equal to or less than the diameter of the cartridge case body.
See more here
Investment Casting: A type of casting using wax molds, Ruger employed this for their 1st revolver and have been casting frames and receivers for other gun makers since the 1960's.
Sintering: A casting process of sorts. Sintered (powdered) metal is placed in a mold and the mold is heated to melt and fuse the metal together. The process was used by Winchester on the model 94 receivers from 1964 to 1982 when they returned to forged receivers
Stock: This can have multiple meanings. It could mean that the gun in question has not been altered from the way it left the factory. It could also describe the wood or synthetic piece that you use to hold a rifle's barreled action. Some people also use the word "stocks" to refer to the grip panels on a handgun (in lieu of the word "grips"). A rifle stock has a few parts:
The barrel channel: This is where the barrel rests, usually about 1/2 the barrel's diameter rests below the top edge of the stock
The Fore end: Some times this is a separate piece of wood, as in the case of a lever action gun, it also refers to the part under the barrel held by the forward hand.
The Butt: As you might guess, this is the back end of the stock, the part that rests against your shoulder.
The Comb: This is the top edge of the back of the stock, the part in which you rest your cheek against when firing.
The Heal: This is the top of the Butt end of the stock.
The Toe: This is the bottom end of the Butt end of the stock.
The Wrist: This is the part your trigger hand grips the stock with, sometimes it is flat, sometimes it is pistol grip shaped.
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