heat
• Softens the bullet, forcing it to conform to the shape of the inside of the gun barrel.
How is a shotgun shell different? A shotgun shell is slightly different; instead of a slug, it contains:
• A primer;
• A load of gunpowder;
• Pellets called shot;
• Wads, pieces of cardboard or paper packed in the shell between the primer and the powder and between the powder and the shot.
In shotgun shells that are reloaded at home (check a large gun reference book for more about that), the wadding often is punched out of magazine pages. Many years ago in London, a police officer was murdered. At the scene, other officers found a partially burned fragment of the wadding, which came from an identifiable newspaper three years old. The search for the suspect continued for several years, but when a suspect was finally developed, officers located at his home both the pages the wadding was punched out of and additional shells loaded with wadding from those pages. This evidence proved to be the vital link to convicting the culprit. That sounds good to me. There's no reason you can't reuse it in fiction.
Rifling
With the exception of the shotgun, all these weapons have rifled barrels. Rifling, which was developed about five hundred years ago, consists of a series of wide spiral grooves cut into the gun-barrel. These grooves, by causing the basically cigar-shaped bullet to spiral through the air much the way a properly thrown football does, greatly improve the accuracy of flight; a smooth-bore firearm is extremely inaccurate at distances of over about eighty feet. (Now you know why you never could hit the side of a barn with a BB gun. It's smooth-bore.) The raised spaces between the grooves in the barrel are called lands. Because the heated slug conforms to and mirrors the shape of the inside of the barrel, the grooves will show up on the soft lead of the bullet (or slug) as shallow raised areas; the lands show up on the bullet as grooves cut into it. Although theoretically all the rifling on firearms manufactured in the same batch should be identical, actually, even to start with, there are microscopic differences, because the rifling equipment is worn slightly more with each barrel it rifles.
The more the firearm is fired, the more pronounced those differences become, as the inside of the barrel, reacting to the heat and the friction of the lead rushing through it, continues to wear. This means that it is possible to identify the slug that went through any given barrel. In practice, this means that it is usually possible to tell what slug was fired from any given gun. Although barrels in some firearms are interchangeable, rarely does anybody switch them—but a recent novel had a delightful scene in which a professional killer committed a murder and then he immediately disassembled his weapon, dropped the barrel and firing pin overboard into the Pacific Ocean, attached a new barrel and firing pin, and went on about his business.
In general, criminals don't do that. The pros might.
In real life: This is not to say there has never been a question as to whether a particular barrel was originally on a particular gun. In the still-controversial Sacco-Vanzetti case, there is no doubt that a barrel that is now on one of the revolvers in the case is the one through which the allegedly fatal bullet was fired, and that the revolvers were in the possession of Sacco and Vanzetti when they were arrested. What does remain in question, however, is whether those particular barrels were on those particular revolvers at the time, and whether the bullet that was presented in court was the one that killed either of the men or one that was later substituted. Proper chain of custody would have prevented those questions from arising.
The Examiner's Role
The arrangement of lands and grooves and the twist of the spiraling vary according to the caliber, make and model of a firearm. So, faced with an undamaged or lightly damaged slug
• Softens the bullet, forcing it to conform to the shape of the inside of the gun barrel.
How is a shotgun shell different? A shotgun shell is slightly different; instead of a slug, it contains:
• A primer;
• A load of gunpowder;
• Pellets called shot;
• Wads, pieces of cardboard or paper packed in the shell between the primer and the powder and between the powder and the shot.
In shotgun shells that are reloaded at home (check a large gun reference book for more about that), the wadding often is punched out of magazine pages. Many years ago in London, a police officer was murdered. At the scene, other officers found a partially burned fragment of the wadding, which came from an identifiable newspaper three years old. The search for the suspect continued for several years, but when a suspect was finally developed, officers located at his home both the pages the wadding was punched out of and additional shells loaded with wadding from those pages. This evidence proved to be the vital link to convicting the culprit. That sounds good to me. There's no reason you can't reuse it in fiction.
Rifling
With the exception of the shotgun, all these weapons have rifled barrels. Rifling, which was developed about five hundred years ago, consists of a series of wide spiral grooves cut into the gun-barrel. These grooves, by causing the basically cigar-shaped bullet to spiral through the air much the way a properly thrown football does, greatly improve the accuracy of flight; a smooth-bore firearm is extremely inaccurate at distances of over about eighty feet. (Now you know why you never could hit the side of a barn with a BB gun. It's smooth-bore.) The raised spaces between the grooves in the barrel are called lands. Because the heated slug conforms to and mirrors the shape of the inside of the barrel, the grooves will show up on the soft lead of the bullet (or slug) as shallow raised areas; the lands show up on the bullet as grooves cut into it. Although theoretically all the rifling on firearms manufactured in the same batch should be identical, actually, even to start with, there are microscopic differences, because the rifling equipment is worn slightly more with each barrel it rifles.
The more the firearm is fired, the more pronounced those differences become, as the inside of the barrel, reacting to the heat and the friction of the lead rushing through it, continues to wear. This means that it is possible to identify the slug that went through any given barrel. In practice, this means that it is usually possible to tell what slug was fired from any given gun. Although barrels in some firearms are interchangeable, rarely does anybody switch them—but a recent novel had a delightful scene in which a professional killer committed a murder and then he immediately disassembled his weapon, dropped the barrel and firing pin overboard into the Pacific Ocean, attached a new barrel and firing pin, and went on about his business.
In general, criminals don't do that. The pros might.
In real life: This is not to say there has never been a question as to whether a particular barrel was originally on a particular gun. In the still-controversial Sacco-Vanzetti case, there is no doubt that a barrel that is now on one of the revolvers in the case is the one through which the allegedly fatal bullet was fired, and that the revolvers were in the possession of Sacco and Vanzetti when they were arrested. What does remain in question, however, is whether those particular barrels were on those particular revolvers at the time, and whether the bullet that was presented in court was the one that killed either of the men or one that was later substituted. Proper chain of custody would have prevented those questions from arising.
The Examiner's Role
The arrangement of lands and grooves and the twist of the spiraling vary according to the caliber, make and model of a firearm. So, faced with an undamaged or lightly damaged slug
Similar Books
