Calibers and Gauges
Even if you are not very familiar with firearms, you might be required or want to write about them. But there is a lot of terminology and it can be very confusing. This is especially true of cartridge calibers and shell sizes. A popular choice for clueless writers is to simply assume that higher numbers means more dangerous or to just use rounds that they have heard about in other sources without understanding what they are talking about. Here are some helpful things to know-
1. They are called cartridges or rounds, not bullets, until they've been fired. In fiction, people usually use the term bullet when they mean cartridge. The bullet is the projectile part that is fired from the gun and hits a target. The cartridge is the bullet seated in a brass casing that is loaded with powder with a small high explosive at the back of the casing that is detonated by the firing pin. The small high explosive is called a primer. The casing is the part that is ejected from the gun, usually up and to the right, or is emptied out before the gun is reloaded.
2. Shotguns use shells. This is because most shotguns do not fire a single projectile, but several smaller projectiles that spread (a small amount, not the huge spread popular in movies) when they are fired. A shell contains a metal back piece with the primer. This is connected to a plastic or paper tube (frequently green or red). The tube is filled with powder in the back and a group of metal balls backed into a small bag in the front. Usually a plug separates the two, it is called a wad.
3. The number in a cartridge's name is called the caliber. It can be misleading. It does not mean anything about the rounds power and some numbers can sound higher "so they must be better right" but are actually higher? The caliber is actually just a measure of the bullet's diameter. It is either in English units or Metric. When in English units it will usually be written with a period than a number. This is the diameter's measurement in inches. For example, a .22 Long Rifle, is 0.22 inches in diameter. A .45 ACP is 0.45 inches in diameter. Metric measurements will be given in millimeters, such as the 9 mm Parabellum. They are also sometimes called by the caliber of the bullet and the length of the whole cartridge. For example, 7.62x39mm.
3.1 When the name is said though, the decimal is not said and the second part of the bullet name may be dropped. So those two rounds would be said "22 Long Rifle or just 22" and "45 ACP or just 45". This convention of just saying the caliber can be confusing when multiple different cartridges of the same size are made. For example the .45 Colt and .45 ACP.
3.2 Just because three numbers are given does not mean that the bullet is larger. For example, a .223 Remington has a smaller diameter than a .45 Colt, even though the the first is said "223" and the second is said "45".
3.3 The naming conventions have not always been consistent, sometimes it was the size of the cartridge and sometimes the size of the casing, which might be slightly larger. For example, the .38 Special and .357 magnum are the same size for this reason. The first is based upon the case size and the second on the bullet size.
3.4 A helpful point of reference between metric and English is the 9mm Parabellum and the .357 magnum. The 9mm and the .357 magnum are very close to the same diameter. They are however, very different cartridges.
3.5 Some rounds have multiple names. Most commonly military rounds that are also produced for civilians firearms or cartridges made in different places. The most common is probably the NATO 5.56 mm and the .223 Remington, with are variants of the military and civilian variants of the same cartridge.
3.6 The term magnum implies that the round is a more powerful cartridge than other cartridges of the same size. This is not always true, but is a good guideline.
4. The size of the bullet will give some indication of how big a hole it will make and therefore how dangerous it will be, but it is not the only or necessarily the most important factor. The M-16 fires a 5.56 mm (or .223 Remington) that is in many ways more dangerous than a .38 Special, which is much larger. Other factors are the speed at which the bullet travels, the shape of the tip, the weight of the bullet, and the stability of the bullet. Bullets work by transferring energy and momentum to a target. Some bullets, such as the 5.56 mm, do this by starting to tumble to create a bigger wound than the caliber would indicate.
5. Shotguns use gauges rather than calibers. This has a very counterintuitive naming system. The Smaller the Gauge, the larger the shotgun barrel. This comes from an old way of measuring barrels and represents the number of solid lead spheres of the same diameter as the barrel that can be made from a pound of lead. Therefore, a 12 gauge is larger than a 20 gauge (the two common shotgun gauges). For reference, a 12 gauge is .729 caliber and a 20 gauge is .665 caliber.
6. There is usually a distinction made between pistol ammo and rifle ammo. Though the two overlap some and cartridges originally designed for one type of weapon might be used in another.
Generally, pistol ammo will be smaller and have relatively straight cylinder shaped casings. Pistol ammo is used by submachine guns, such as Uzi's or Tommy Guns.
Rifle ammo tends to be much longer and larger. It is very common for rifle cartridges to have tapered sides and to have a bottleneck near the bullet. They are usually used in assault rifles, hunting rifles, sniper rifles and in larger machine guns.
7. Two types of common bullets are used for handguns (there are probably more variants then I can think of, but I'm only covering these two). Full Metal Jackets (FMJ) and Jacketed Hollow Points (JHP), sometimes just called Hollow Points. FMJs are a lead bullet with a metal jacket (usually of a copper-nickel alloy). The metal jacket prevents damage to the barrel or lead build up. They make a hole of about their own size. JHP have a recess in the front of the bullet. They are designed to catch in a target then expand outward in a mushroom shape so that they cause more damage. JHP are not frequently used for military purposes, but are popular among police forces because they are less likely to overpenetrate (go through the person being shot and hit something or someone behind them).
8. Shotguns fire two different types of ammo regularly, shot and slugs. Shot is small pellets. Bird shot is very small circular pellets, typically 1/6" or less. These are not designed to penetrate large targets and will generally only go 1-3 inches into a person. A shot from birdshot is very survivable. Buckshot is larger circular pellets, typically 1/4" or greater. (double ought is 1/3" for those that are curious) It tends to be much more deadly than birdshot. Slugs are solid lead projectiles that replace the packed pellets in a normal round. They tend to be less accurate at long ranges, but because they are heavy and large in diameter can be very dangerous. They are designed for hunting large game.
Hope that makes some sense of calibers for you. Below is a list of some common cartridges ranked by the amount of energy they typically deliver from lowest to highest. (Energy does not necessarily mean how deadly they are, but it does give some idea and also gives an indication of how much penetration potential they have)
Pistol Rounds
1. .22 Long Rifle (popular for small game and target shooting)
2. .38 special (a lot of old style police revolvers fire these)
3. 9 mm Parabellum (Glocks and Berettas are frequently chambered in 9mm)
4. .45 Colt (A popular revolver round coming down from the Colt Single Action Army revolver of the 1800's. Modern loadings are more powerful)
5. .45 ACP (Automatic Colt Pistol, used by Tommy guns and 1911s)
6. .357 magnum (a more powerful replacement for the .38 special)
7. .44 magnum (Dirty Harry's weapon of choice)
Rifle Rounds
1. .223 Remington (5.56 mm) (The M-16's round)
2. 7.62x39mm (The AK-47's round)
3. .308 Winchester (7.62x51mm NATO) (Used by the M-14 and is popular for police sniper rifles and hunters.
4. .30-06 Springfield (Here the 06 designates 1906. This is the round used by Springfield M1906, during World War I, and used in the M1 Garand in World War II)
5. .300 Win Mag (A more powerful rifle round for hunting large game like bears)
6. .50 BMG (Also called a 50 Cal. It is designed for penetrating engine blocks and damage other material targets, to be fired by heavy machine guns. It is also frequently used by snipers)
Thursday, December 15, 2011
Tuesday, December 13, 2011
A Helpful Guide to Guns in Fiction, Part 1
Subsonic Ammunition
This label is frequently bandied about as a magic type of stealth ammunition. Subsonic ammunition does not have the associated "sonic boom" that super sonic ammunition does. This can be achieved with a heavier bullet (the part that actually shoots out of the gun, the whole thing is a cartridge) and/or with a smaller cartridge load. As an intelligent person might suspect, like most "stealth" bullets these don't work the way they are often portrayed. Things that would be helpful to know.
1. Many pistol rounds are already subsonic in most of the loads they are normally fired in. The .38 special for example is ~300 m/s while the speed of sound is ~340 m/s. They still make noise.
2. The subsonic designation is only useful for rounds that typically sit right around the speed of sound for normal loadings. Such as the 9 mm Parabellum round. It can go from 400-300 m/s. For this round, there is a difference in noise between different types of rounds, but they never make a "whisper". There is always going to be noise. They just do not make the characteristic ballistic crack.
3. Subsonic variants of ammunition always have shorter effective ranges than their supersonic equivalents and frequently will have less penetrating power. This is because a slower moving bullet will not travel as far before it is noticeably effected by gravity and experiences significant drop. This might be offset some by a heavier bullet holding more energy.
4. Some cartridges would never be loaded to be subsonic in anything but practice rounds. A .357 magnum round for example. It is well above the speed of sound ~400 m/s and was designed to be so. It would be possible to load it to be sub sonic, but in practice it would be easier to simply get a .38 special round, which will fit a .357 magnum chamber and is already subsonic. This is not to say that people haven't, just that it does not make sense for your military black ops guys to do so.
5. Some automatic and semi-automatic rounds may have trouble with subsonic cartridges. This is because the energy to cycle the weapon for the next shot comes from the cartridge and subsonic cartridges usually have less energy. It is probably safe to assume that your characters have tested their weapons with the ammunition they plan to use off page and so this may not be a problem, but it is something to be aware of.
6. Rifle rounds will never be loaded with subsonic rounds (at least modern rifles, black powder rifles are a different story). It defeats the purpose of a rifle round. Rifles typically fire bullets going 2-3 times the speed of sound. Reducing their speed below the speed of sound reduces their energy by at least a factor of 4 (energy varies with the square of the velocity) and similarly reduces their penetrating power. There is no reason that anyone would do this. They could get a submachine gun or pistol that would be just as deadly, have the same range, be lighter, and have easier to handle ammunition. This includes assault rifles such as the AK-47 and M-16. Again, you can find people that have done this and even people that make subsonic rounds for those weapons, but they do not function like a normal rifle and you can expect problems cycling the weapon with loads that have been so far reduced. Also, the sights for those weapons would be based upon the higher velocity so range adjustments would be unreliable.
Note: There are some types of rifle ammunition that are designed to fire subsonic rounds or even pistol rounds. The subsonic rifle cartridges tend to have much heavier bullets than their supersonic counterparts and rifles that fire pistol ammo are designed for higher accuracy and range with the pistol ammo. And there is nothing wrong with them, but they would not normally be labeled "subsonic ammo". A possible exception to this is the .300 Whisper, which can be either supersonic or subsonic variants. However, subsonic variants weigh nearly twice as much and deliver less than half as much energy. It depends upon making a large hole rather than going deep and delivers as much kick as a .45 handgun round.
7. To give an idea of the impact of subsonic rounds consider two rounds, one that is just barely subsonic at 340 m/s (depending upon the air conditions this may or may not be subsonic and even this close to sonic speeds you are likely to get some ballistic crack) and another that is a more standard M-16 round going 990 m/s. Both are fired at a target on level ground 100 meters away. It takes the 340 m/s round 0.294 seconds to reach the target and in that time drops 0.424 meters (about 16.7 inches). It takes the 990 m/s round 0.101 seconds to reach the target and in that time drops just 0.0500 meters (about 1.97 inches). If you're going to be off by 2 inches on a shot, you don't need to correct to hit your target, but 16-17 inches requires adjustment that can be difficult. Additionally, the longer flight time allows more time for crosswind to effect the shot and drag would slow the bullets causing even more drop. Subsonic rounds are only effective at short ranges. At ranges shorter than 50 meters, the drop is less than 4 inches and could be considered reliable in hitting targets. Note, bullet drop is not the only measure of problems that can be encountered and many rifles have sights to account for bullet drop.
8. Similarly, if a target is hit by the subsonic round in the above example, a standard bullet proof vest would likely stop the round. The standard round penetrates a bullet proof vest.
9. Snipers would NOT use subsonic rounds. Subsonic rounds are for short ranges, snipers need accurate fast moving rounds so they can hit from far away while staying hidden (see number 7). This is a personal pet peeve, a sniper in fiction on a roof a block away using subsonic rounds so they cannot be found and shooting people right and left. If they are close enough to be using subsonic rounds, then they are not really a sniper, but a concealed shooter. Military sniper rifles require all rounds to be put into a one inch circle at 100 meters and this is not possible with subsonic rounds.
Hopefully this has been helpful for your writing. Other topics that will be covered. Bullet penetration (including vests and bullet proof material). Rifles versus pistols and an explanation of caliber.
This label is frequently bandied about as a magic type of stealth ammunition. Subsonic ammunition does not have the associated "sonic boom" that super sonic ammunition does. This can be achieved with a heavier bullet (the part that actually shoots out of the gun, the whole thing is a cartridge) and/or with a smaller cartridge load. As an intelligent person might suspect, like most "stealth" bullets these don't work the way they are often portrayed. Things that would be helpful to know.
1. Many pistol rounds are already subsonic in most of the loads they are normally fired in. The .38 special for example is ~300 m/s while the speed of sound is ~340 m/s. They still make noise.
2. The subsonic designation is only useful for rounds that typically sit right around the speed of sound for normal loadings. Such as the 9 mm Parabellum round. It can go from 400-300 m/s. For this round, there is a difference in noise between different types of rounds, but they never make a "whisper". There is always going to be noise. They just do not make the characteristic ballistic crack.
3. Subsonic variants of ammunition always have shorter effective ranges than their supersonic equivalents and frequently will have less penetrating power. This is because a slower moving bullet will not travel as far before it is noticeably effected by gravity and experiences significant drop. This might be offset some by a heavier bullet holding more energy.
4. Some cartridges would never be loaded to be subsonic in anything but practice rounds. A .357 magnum round for example. It is well above the speed of sound ~400 m/s and was designed to be so. It would be possible to load it to be sub sonic, but in practice it would be easier to simply get a .38 special round, which will fit a .357 magnum chamber and is already subsonic. This is not to say that people haven't, just that it does not make sense for your military black ops guys to do so.
5. Some automatic and semi-automatic rounds may have trouble with subsonic cartridges. This is because the energy to cycle the weapon for the next shot comes from the cartridge and subsonic cartridges usually have less energy. It is probably safe to assume that your characters have tested their weapons with the ammunition they plan to use off page and so this may not be a problem, but it is something to be aware of.
6. Rifle rounds will never be loaded with subsonic rounds (at least modern rifles, black powder rifles are a different story). It defeats the purpose of a rifle round. Rifles typically fire bullets going 2-3 times the speed of sound. Reducing their speed below the speed of sound reduces their energy by at least a factor of 4 (energy varies with the square of the velocity) and similarly reduces their penetrating power. There is no reason that anyone would do this. They could get a submachine gun or pistol that would be just as deadly, have the same range, be lighter, and have easier to handle ammunition. This includes assault rifles such as the AK-47 and M-16. Again, you can find people that have done this and even people that make subsonic rounds for those weapons, but they do not function like a normal rifle and you can expect problems cycling the weapon with loads that have been so far reduced. Also, the sights for those weapons would be based upon the higher velocity so range adjustments would be unreliable.
Note: There are some types of rifle ammunition that are designed to fire subsonic rounds or even pistol rounds. The subsonic rifle cartridges tend to have much heavier bullets than their supersonic counterparts and rifles that fire pistol ammo are designed for higher accuracy and range with the pistol ammo. And there is nothing wrong with them, but they would not normally be labeled "subsonic ammo". A possible exception to this is the .300 Whisper, which can be either supersonic or subsonic variants. However, subsonic variants weigh nearly twice as much and deliver less than half as much energy. It depends upon making a large hole rather than going deep and delivers as much kick as a .45 handgun round.
7. To give an idea of the impact of subsonic rounds consider two rounds, one that is just barely subsonic at 340 m/s (depending upon the air conditions this may or may not be subsonic and even this close to sonic speeds you are likely to get some ballistic crack) and another that is a more standard M-16 round going 990 m/s. Both are fired at a target on level ground 100 meters away. It takes the 340 m/s round 0.294 seconds to reach the target and in that time drops 0.424 meters (about 16.7 inches). It takes the 990 m/s round 0.101 seconds to reach the target and in that time drops just 0.0500 meters (about 1.97 inches). If you're going to be off by 2 inches on a shot, you don't need to correct to hit your target, but 16-17 inches requires adjustment that can be difficult. Additionally, the longer flight time allows more time for crosswind to effect the shot and drag would slow the bullets causing even more drop. Subsonic rounds are only effective at short ranges. At ranges shorter than 50 meters, the drop is less than 4 inches and could be considered reliable in hitting targets. Note, bullet drop is not the only measure of problems that can be encountered and many rifles have sights to account for bullet drop.
8. Similarly, if a target is hit by the subsonic round in the above example, a standard bullet proof vest would likely stop the round. The standard round penetrates a bullet proof vest.
9. Snipers would NOT use subsonic rounds. Subsonic rounds are for short ranges, snipers need accurate fast moving rounds so they can hit from far away while staying hidden (see number 7). This is a personal pet peeve, a sniper in fiction on a roof a block away using subsonic rounds so they cannot be found and shooting people right and left. If they are close enough to be using subsonic rounds, then they are not really a sniper, but a concealed shooter. Military sniper rifles require all rounds to be put into a one inch circle at 100 meters and this is not possible with subsonic rounds.
Hopefully this has been helpful for your writing. Other topics that will be covered. Bullet penetration (including vests and bullet proof material). Rifles versus pistols and an explanation of caliber.
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