Guns - A Brief Summary of Terms

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Guns represent the latest of evolutions in mankind's pursuit of effective ways to end lives. Make no mistake, the gun was designed to kill, pure and simple, though a number of sports and non-lethal recreational activites have evolved around them. All modern variations of the firearm evolve from the ancient harquebus (a primitive rifle) and hand cannons found in the late 13th and early 14th centuries. Despite various differences in mechanical design, projectile, purpose, and appearance, all guns share a common denominator. They are designed to, at the wielder's behest, propel an object through a tube at a target.

Despite the misgivings surrounding these weapons the world over, a wise researcher must understand that it's hard to successfully negotiate socio-political viewpoints while staring down the barrel of a Beretta 9mm. Therefore, one would be wise to learn a bit about firearms and perhaps undertake a bit of training in the usage of one, just in case the necessity arises.

Types of Firearms


The term pistol describes a firearm that can be held, cocked, and fired effectively in one hand. Pistols are either 'automatics' (chamber-fed by a magazine) or a 'revolver' (rounds pre-chambered in a rotating cylinder). Pistols typically weigh less than five pounds, are most effective at 30ft (10m) or less, and fire less powerful and less accurate rounds than their rifle cousins. Automatic pistols include the M9 Beretta and the M1911A1 Colt .45. Revolvers include the Colt .357 Magnum and the .38 Smith and Wesson 'Police Special'.

Machine Pistols

Machine pistols are pistols which, by virtue of their design, will continue to expend ammunition at a high rate of speed as long as the trigger is depressed. Machine pistols can be fired in one hand, but their accuracy is severely compromised. They are magazine fed, and typically fire on automatic. Two common machine pistols are the Israeli Uzi 9mm and the Ingram Mac-10.


Rifles represent the heavier end of the firearm spectrum. Rifles come in two forms, semi-automatic and bolt-action. Semi-automatic rifles are magazine or 'clip' fed, each pull of the trigger discharging a round, ejecting the spent brass, and feeding a new round into the chamber. Bolt-action rifles require the shooter to manipulate the 'bolt' of the rifle by hand, in order to fire another round. Rifles weigh between six and twenty-seven pounds (2.72 to 12.5 kilos). A carbine is simply a shortened version of an existing rifle. A well-known self-loading rifle is the M1 Garand, circa WWII, while the M1903 Springfield is a classic example of a bolt-action weapon.

Assault Rifles

Assault rifles as discussed here are a type of rifle designed for combat use, especially in close combat military situations. Assault rifles differ from civilian rifles in several aspects. Generally speaking, assault rifles are designed specifically for combat. They have more ergonomic stocks, are lighter, and have a pistol-style handgrip for better control and retention. Assault rifles are designed to be fired at a high rate, either in an automatic mode, a burst mode (3 rounds for each pull on the trigger), or are designed to be fired rapidly at a target without requiring the shooter to remove the weapon from his or her shoulder, necessitating a clip or magazine fed action.

Sub-Machine Guns (SMGs)

Bridging the gap between assault rifles and machine pistols, SMGs are a hybrid of the two. SMGs are designed to be fired with both hands; have a fully automatic rate of fire; and are fed by magazines. They are typically more accurate than machine pistols and more reliable, though do not hit as hard as a rifle of the same calibre. They are very popular among military personnel for their light weight (5-9 lbs), their ease of use, accuracy, and small profile. Examples of SMGs are MP-5s, P-90s, and Thompson .45s.


Shotguns were originally designed as hunting weapons. A shotgun is closely related to a rifle, with a few subtle differences. Breech-loading shotguns, the most primitive style of the weapon, are loaded by opening a latched hinge where the barrel meets the stock and trigger. A 'shell', a special shotgun round, is inserted directly into the chamber, the breech is closed, and the trigger strikes the back of the shell. Pump-action shotguns have an internal cylinder magazine. Both styles of shotguns are typically 'smooth bore'. By drawing back on the 'pump' mechanism, spent shell casings are ejected and a new one is advanced into place. Both styles of shotgun fire either 'shot' or 'sabot' rounds, which will be covered furthur in this entry.

Machine Guns

Machine guns are essentially rifles, but designed to fire on a fully-automatic basis. Though they can be used effectively on a semi-automatic setting, they are most effective in laying down fire upon a large sector, either as a defensive device or in support of an advance. Light machine guns are those defined as being 'man-portable', heavy machine guns requiring either a stationary platform or vehicle mounting. Machine guns are generally fed by 'belts' of ammunition, though magazine-fed machine guns exist. Examples of machine guns are the German MG-42, the American M-60, the 240-B, and the Mk. II .50 Cal.

Pieces and Parts

Nearly all firearms share certain common factors. Knowing the terminology associated with these factors will make it not only easier to converse about firearms, but understand the differences in design and the relative effectiveness of a weapon.

Round (Cartridge and Bullet)

A cartridge is, with a few exceptions, the item placed in a firearm that does the killing. It's typically a cylinder of brass, anywhere between a quarter of an inch in length (5mm) to nearly four inches (99mm). At the back of the brass cylinder is a tiny blasting cap. Opposite, there is a harder, unattached metal object that is the actual 'bullet' that exits the barrel of the weapon. When the blasting cap is struck by the hammer of the weapon, it causes the powder within to rapidly combust. The resulting expansion of gas forces the bullet out of the barrel at great speed. The mass of a bullet is weighed in grains. A standard M-16 bullet is approximately 62 grains, while a .50 calibre bullet, the largest man-portable round, is nearly 671 grains.


Calibre is the byword among all firearms. Calibre measures, in American inches or SI, the diameter of a bullet. Calibre tends to vary between countries, manufacturers, and weapons. When describing calibre in American terms, a .223 calibre round is .223 parts of one inch. When considering more technically accurate dimensions of a round, the SI definition is more useful. A .223 calibre round is measured as being 5.56x45mm, or a bullet 5.56mm in diameter, set inside of a cartridge measuring 45 mm in length. This is much more useful for accurately describing the size of a specific kind of ammunition, as opposed to the American description which is much more general and usually relates to the bore size of the weapon, rather than the round itself. A .223 calibre rifle such as the M16 fires a 5.56 mm round, though this round is closer to .21 inches in diameter.

Gauge (Shotguns)

Shotgun shells are a special kind of ammunition fired in only those weapons. The caliber of shotguns is measured in terms of gauge or bore (the British English term). The gauge number is determined by the number of solid spheres of a diameter equal to the inside diameter of the barrel that could be made from a pound of lead. So a 10 gauge shotgun has an inside diameter equal to that of a sphere made from one-tenth of a pound of lead. Common gauges are 10, 12, and 20, as well as the .410.

Shotgun Shells: Sabot/Slugs

Shotguns fire one of three basic rounds for hunting, combat, and sport purposes. The heaviest round, the 'sabot' or slug round, is essentially a large, bulky bullet with a breakaway plastic sleeve that it sheds once leaving the barrel. Slugs have the disadvantage of losing their airspeed extremely rapidly and being notoriously difficult to aim at ranges over 100m, due to their bulky design. However, at any range, slugs inflict massive damage due to their sheer mass and speed. A typical 12 gauge shotgun round is a blunt one-ounce hunk of metal that is roughly described as a .750 calibre round weighing 432 grains (appx. 28 grams). A standard deer rifle round, the .308 calibre (7.62x39mm), is only 150 grains.

Shotguns: Buckshot and Shot

For hunting varmint sized animals (20 lbs or less) or fowl, the preferred ammunition for a shotgun is a buckshot or shot shell. This ammunition is actually a hefty powder charge in a hard plastic cylinder behind anywhere from nine to a hundred metal spheres, depending on the shot number. Buckshot comes in several sizes, from #4 (each pellet .24 inches in diameter), down to #000 (triple-aught buck), which has .36 inch pellets. Birdshot is typically considered anything that can be simply weighed into a shell rather than requiring hand-stacking, from #12 size (.05 inch pellets) to #2 (.15 inches) and BBs (.18 inches).


The bolt is the device that causes the bullet in rifles and SMGs to slide forward into the chamber. When the round is discharged, semi-automatic weapons automatically push the bolt backwards. This ejects the now empty spent brass cartridge and feed in a new round. Recoiling bolts help to absorb some of the recoil or shock of firing, as well as greatly improving consistent shooting posture and speed of fire.


The portion of a firearm that strikes the rear of the cartridge, causing the powder to ignite and propel the bullet out of the rifle.

Firing Pin

In assault style weapons such as SMGs, machine guns and assault rifles, the hammer is replaced by a small pin inside the bolt of the rifle itself. When the bolt is drawn back to the rear of the rifle and locked in place, the weapon is considered 'charged'. Once the trigger is pulled, the bolt is released and shoots forward, causing the pin to strike the blasting cap at the end of the cartridge and ignite the powder within.


The portion of the firearm in which the cartridge is held, immediately before being discharged. In revolvers, the cylinder itself contains a number of tiny chambers, each holding one bullet within.


In automatic pistols, the uppermost portion of the weapon. When loading and unloading the pistol, one must pull firmly back on the slide to either advance the first round into the chamber or eject a cartridge from the chamber, when loading and unloading. Each time the weapon is fired, the slide kicks backwards and performs both of these actions automatically.


A magazine is an evolution from the old clips that created the first truly semi-automatic rifles. A magazine is a fully enclosed metal or heat-resistant plastic casing that holds a number of rounds stacked on top of one another. The magazine is inserted into the weapon where spring tension from the base of the magazine presses the rounds against the base of the chamber. As the chamber slides open, the rounds are automatically fed into the chamber itself each time the empty chamber is presented.


An older style of the magazine. Where magazines can hold often as many as 30 rounds at a time in a contained structure, clips held usually no more than ten rounds at a time. Clips left most of the round within exposed, being designed to only grab the 'base' of the rounds, and had to be fully inserted into a weapon, such as the M1 Garand.


With revolvers, there is no magazine or chamber, per se. Instead, there is a metal cylinder between the hammer and the barrel, with between four and twelve small holes in it. Each hole contains a round. When the cylinder is locked in place and the hammer drawn back, a hole in the cylinder aligns itself with both the barrel of the weapon and the hammer. Once fired, the cylinder rotates and automatically aligns the next chamber- and next round- with the hammer.


This describes the way the interior of a barrel is grooved. Putting rifling inside of a barrel in a corkscrew manner causes the bullets to rotate in their flight path, giving them a greater degree of accuracy. The rifling number indicates the number of grooves, while the ratio is the number of full rotations made in a given length. A 1:11 ratio, for example, means that the rifling makes one full rotation in eleven inches. When bullets pass through the barrel they are grooved according to the rifling pattern inside the barrel. All rifling patterns are unique, similar to a fingerprint.


The act of drawing back the hammer of a weapon in preparation of firing the weapon. This can also mean loading a round into the chamber, as with several weapons the act of cocking them loads as well. In terms of SMGs, machine guns, and assault rifles, cocking the weapon is known as 'charging' it, which means locking the bolt in place in preparation of firing.

Minute of Angle (MOA)

This is a specific statement regarding the accuracy of a weapon. Without getting into the math, a value of 1 MOA is equivalent to 1.047 inches at 100 yards. Therefore, given ideal shooting conditions and discounting human error, a weapon with an MOA of 1 will put every round within a 1.047-inch circle at a distance of 100 yards. This becomes a 2.094 inch circle at 200 yards, 3.1 inches at 300, etc.

Muzzle Brake

A muzzle brake is designed to control both the light flash of a discharged round and the direction of the gasses exiting the barrel. Instead of belting the gasses forward directly out of the weapon, it vents them to the sides and slightly rearward, compensating for both the climb of the rifle and the recoil, or force of the fired round, itself.



Many rifles still require the bolt to be manually pulled to the rear, rotated, then moved forward again in order to eject spent brass, advance a round, and move the next round into the chamber. This is known as a bolt action rifle.


Shotguns that require the pumping mechanism to load and unload ammunition are considered to be 'pump action'. Pump action shotguns have an internal magazine which feeds a new shell into the chamber each time the action works, hence the name.

Single Action

Single Action revolvers must be manually cocked for each shot- that is, the hammer must be drawn back in order to spin the revolver cylinder around and position the next round in front of the hammer. This mode improves accuracy but slows the fire rate. For semi-auto pistols, Single Action means that the pistol must be manually cocked for the first shot (usually, this is done by pulling the 'slide' - this action cocks the hammer and feeds a cartridge into the chamber). For the second, and all consecutive shots, cocking is done automatically, when recoil force pulls back the slide.

Double Action

Double Action for the revolver means that the hammer for each (including the first) shot is automatically cocked by trigger pull (this action also rotates the cylinder to the next position). This mode speeds up the firing rate and simplifies shooting actions, but greatly increases trigger pull (from the 2.2-4.4 lbs usually found in single-actions, to 8.8-12.2 lbs in double-actions). For semi-automatic pistols, this means that only the first round must be manually fed into the chamber- all following rounds are fed automatically and the hammer re-cocked with each shot (hence the pistol term, 'automatic').


Automatic pistols, not to be confused with machine pistols, have the simple expedient of not requiring cocking between rounds. The rearward force that the bullet generates when expended is sufficient to push the slide back, eject the spent brass, and allow a new round to be loaded.


Any weapon which does not require reloading, hand-chambering, or re-cocking between expended rounds is considered semi-automatic. One round is expended each time the trigger is pulled.


By holding down the trigger mechanism, the weapon will discharge ammunition continuously until either the magazine/belt is emptied or there is a mechanical failure with the weapon.

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