Friday, October 29, 2010

Bullets

One of the things I’ve seen the most in writer’s forums is confusion about the type of gun vs. the type of round.  I’d like to hit that part first.

A 9mm Parabellum has no idea whether it’s begin fired from a Glock, a single shot Contender, or an MP5 submachine gun.  When people ask for a powerful handgun, someone almost always bring up a Glock, but never mentions the caliber.  This is a danger sign.  Don’t listen to these people.

There is no real difference in power between the Desert Eagle in .44 magnum and the Smith and Wesson revolver Dirty Harry used to teach basic math in 1971.  If they have the same powder charge and the same bullet, they will have basically the same effects.

So, what does “caliber” mean?


Caliber is the measure of the outside diameter of the bullet, and it’s the NUMBER ONE area where a crime writer can mess up a detail.  This is especially true for a police procedural style story.  When the medical examiner digs the bullet out of the victim, and says it was a .38, he’s guessing.  There is no way to tell the difference between a 38 an a 357 by looking at the bullet alone.  For that matter, it could also be a .357 Sig, which a pistol round that has a bottle shape like a rifle.  The same goes for all variants of the 9mm family.  9mm Parabellum (9X19), 380 auto (9X17), 9mm Makarov (9X18), and 9x21 can all fire the exact same bullet.  It gets worse.

The difference in diameter between a .357 and a 9mm is 0.002 inches, or about the thickness of a sheet of paper.  Next time your favorite detective spots a hole in the wall and says it was made by a any of the above, smack them.

Now, it might be possible to narrow down the caliber by seeing the actual bullet.  38/357 bullets tend to be the heaviest, while the .380 tend to be the lightest.  There is some overlap possible, but with the actual slug in hand, it might be possible to rule out the extreme ends.  More on that below.

Caliber is measured in either inches or millimeters.  Weight of the bullet is measured in grains or grams.  There are 7000 grains to a pound.  I’d have to look up grams, but it’s close enough to 453.6 that we can use that for now.

There are four factors that determine how effective a bullet could be.
  1. Diameter determines the size of the hole it makes in the target.  Nearly all realistic weapons are going to be between 0.223 inches and 0.500 inches.  That’s 5.56mm to 12.7mm.
  2. Speed is the more significant factor in how hard a given bullet hits the target.  If a brick has to hit my foot, I'd rather it be set there than dropped from a ten foot ladder.  Most bullets will go from 800 to 3500 feet per second.  That's 244 to 1067 meters per second.
  3. Weight is the other.  Heavier bullets will do more damage for a given speed than slow ones.  A light .22 long rifle bullet is 32 grains (2 grams) to 750 grains (48.5 grams) for an elephant gun.
  4. Type of bullet.  Not all bullets are made the same way.  Some are designed to penetrate, while others are designed to expand quickly and stop a short distance into a target.  For most of the calculations, this one doesn’t really matter.
As a writer, it will be important to get the details right.  If your victim is found with a bullet that is 0.357 caliber and 165 grains, it’s probably a .357.  38 Specials rarely use bullets that heavy.  Likewise, few 9mm rounds will be loaded with 88 grain bullets, though both are possible.

This is where a reloading manual can be very helpful.  There are also a number of sites online that will give you the exact information you need.  If I want to arm my killer with something like an old .32 caliber auto, I can do a search for “.32 auto reloading data”.  One of the first sites to come up tells me that there are 60 grain bullets, and 71 grain bullets.  This is what my autopsy report will show.  If I have a .32 caliber bullet that is much different than that, it's either a clue or a mistake.  For the sake of the audience, do it on purpose and make it a clue.

As far as the types of bullet go, there are two main factors.  Materials and shape.

Most modern bullets are a lead core surrounded to some degree by a copper jacket.  The copper helps to seal the bullet off from the burning gas from the powder.  Pure lead bullets are possible but if they go too fast, they will cause problems for the barrel of the gun and suffer from a greatly reduced accuracy.  This is around the 1500 feet per second mark.

Round Nosed are basically just that, bullets that are round on the front.  These are most common in automatic pistols since they suffer the least from feeding issues.  That means they jam less often.  They are less often used in rifles.

Hollow Point have an aura about them for some reason.  Some will claim they are illegal, while others claim that they are the ultimate bullet for any purpose.  Both are false.  A hollow point is just a regular bullet with a cup shaped opening in the front.  When these bullets hit something soft, the tip will open up, like a mushroom.  This makes the wound channel bigger and results in more blood loss.  It also slows the bullet down faster, resulting in a higher energy transfer to the target.  This makes them great for self defense situations, but a poor choice for shooting through something.

In tests, hollow points have been known to get debris stick in the cup turning the bullet into basically a round nose.  Likewise, hollow points that hit something like a door panel of a car will have the sides of the cup flattened down and make the bullet more like a Wadcutter, discussed below.

Wadcutter bullets are mainly used in revolvers for target competitions.  They are almost always straight lead, though some may have a small copper disk on the back, called a Gas Check.  Wadcutters are used primarily in target shooting because the hole they make in the paper is a clean one, with no tearing.  From the side, they look a little like a soda can, with a flat bottom and straight sides right up to the very tip.  The front of the bullet is squared off on the edge, then steps up slightly.  This gives it a nice 90 degree corner and a slight bulge at the front.  They are remarkably difficult to feed properly in an automatic.

Semi-wadcutters are a variant of the above and have a slightly longer nose.  They make a hole with a bit of tearing round the edges, but still much cleaner than any round except a wadcutter.

Frangible Bullets are a relatively new idea, coming to the public eye in the early 1980’s or so.  The idea behind them is that they function just like a regular bullet until they hit something hard, then they turn to dust.  Some use a combination of metal powder and epoxy, while others use a copper cup filled with very small lead shot.  These rounds can be very devastating to living creatures, but will not pass through a single layer of sheetrock used in the walls of most houses.  This makes them ideal for home defense situations and for use on airplanes, but useless for nearly everything else.  They would never get through a car door, and probably would not get through a window intact.

Shot Capsules are special rounds, mostly used in revolvers, but available for automatics as well.  In the revolver version, a thin plastic cup is filled with small lead shot pellets and loaded into the casing.  When the round is fired, the cup will tear apart in the air and the shot will continue on.  This can turn a .44. Magnum into a low volume shotgun.  The main use for this it bird and small game hunting, and snakes.  They can be made at home by anyone with the proper gear.

The automatic version is actually an extended brass casing with a rounded tip.  I had some for a .45 auto and they worked very well, although the second to last round in the magazine always jammed.  Shot capsules will be nearly useless as a self defense round (for reasons explained in the shotgun section), and have a very limited range.  At 25 yards, my .45 managed to make three holes in a man sized paper target.  Each hole was smaller than a pinprick (#12 shot).

Armor Piercing bullets are full metal jacketed bullets, often using a steel core or tip to make getting into a target easier.  The advantage to these bullets is that they hold their shape after impact much better.  That is also their main disadvantage as far as a self defense round goes.  They create the smallest possible wound channel, and tend to pass straight through the target.

Mutli-slug Bullets.  I’m not sure what these are actually called, and they can only be used in very large revolvers.  Large in this case means a long case.  The .357 Maximum (which few have ever heard of) would be a good choice.  I fired them in a .454 Casull.  They would never work in a .45 auto or 9mm.  The idea it to place a small round nose bullet and two short wadcutters in a single casing.  They can also be made with round lead balls as the secondary bullets, though these will not be as accurate.

When the round is fired, all three bullets go down the barrel at once, separating once they hit the air.  The result is three entry wounds with a light bullet as opposed to one from a heavier one.  The total recoil from something like this is the same as firing one heavy bullet, since the mass being pushed is still higher than a normal single round.

Certain factory ammunition will use distinctive bullets.  The long time media darling was the infamous “Black Talon” bullet.  This was sort of like a hollow point in that it would open on impact, but rather than open into a mushroom shape, it would open to reveal six “claws” that would tear through the body.  It was not unheard of for these to actually weigh more after firing due to the tissue stuck in the jagged sections.  This was combined with a design that acted like a round nose as far as penetration went.

Other factory bullets markets for the self defense and police markets are Federal Hydra-Shock, Remington Golden Saber, and Speer Gold Dot.  The only time a report should show a specific make of bullet, it should be something like these, and only in a police procedural type of story where the type of bullets being used by the killer matters for some reason.

While the bullets listed above can be bought fully loaded and ready for use, Gold Dot can be bought as just the bullets and used to reload ammunition.  The specifics of that is a different section as well, but the thing I wanted to touch on here is that if your shell casings are Federal, and your bullets are Golden Saber, it might mean that the killer has “pulled” the bullets from one case to load into another.  Why this would be done is up to the writer, but it is possible to take a loaded round and remove the slug to fire it in something else.  There are ways to do this without putting tool marks on the bullet.

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