Gunshot Wounds

Practical Aspects of Firearms, Ballistics, and Forensic Techniques, Third Edition

Vincent DiMaio

• Publisher: CRC Press
• Year: 2015
• ISBN:
  9781000430158
• Edition: 3
• Topic: Law
• Subtopic: Criminal Law
• Index: Law

Written by the nation's foremost authority on gunshot wounds and forensic techniques as they relate to firearm injuries, this third edition of a bestseller provides critical updates to information on gunshot wounds and the weapons and ammunition used to inflict them. The book describes practical aspects of ballistics, wound ballistics, and the classification of various wounds caused by handguns, rifles, and shotguns. It also explains autopsy techniques and procedures and laboratory analyses relating to weapons and gunshot evidence. A much-needed update after nearly 20 years, the third edition of Gunshot Wounds provides the latest and most thorough information on firearms and best practices for examining firearm-related wounds.

Firearms and Ammunition

1

My wife yes; My dog maybe; My gun never!

Bumper Sticker

There was trouble ‘bout something, and then a lawsuit to settle it; and the suit went agin one of the men, and so he up and shot the man that won the suit—which he would naturally do, of course. Anybody would.

The Adventures of Huckleberry Finn,
Mark Twain

In order to interpret gunshot wounds, a certain basic knowledge of firearms and ammunition is necessary. This chapter will attempt to present such information.

Small Arms

There are five general categories of small arms: handguns, rifles, shotguns, submachine guns, and machine guns. A possible sixth category is personal defense weapons (PDWs).

Handguns

There are four basic types of handguns:

1. Single-shot pistols

2. Derringers

3. Revolvers

4. Autoloading pistols (automatics)

Single-Shot Pistols

A single-shot pistol has one firing chamber integral with the barrel, which must be loaded manually each time the weapon is to be fired (Figure 1.1a).

Derringers

They are a variant of single-shot pistols. Derringers are small pocket firearms having multiple barrels, each of which is loaded and fired separately. The traditional derringer has two barrels (Figure 1.1b).

Revolvers

Until the 1970s, the revolver was the most popular and most common type of handgun in the United States. It has now been replaced in popularity by the autoloading pistol. Revolvers have a revolving cylinder that contains several chambers, each of which holds one cartridge. The cylinder is rotated mechanically so as to align each chamber successively with the barrel and firing pin. The first revolver was produced by Samuel Colt in 1835–1836.

Figure 1.1 (a) Single-shot pistol and (b) derringer. (Photo courtesy of Randall Frost, MD.)

There are three types of revolvers, the most common of which is the “swingout” (Figure 1.2a). On pressing the cylinder latch, normally found on the left side of the frame, and pushing the cylinder to the left, the cylinder swings out, exposing the chambers. Each individual chamber is then loaded with a cartridge. The cylinder is then swung back into the frame, engaging the cylinder latch. The weapon is now ready to be fired. After discharge of all the cartridges, the cylinder latch is pressed and the cylinder is swung out. An ejector rod, affixed to the front of the cylinder, is pressed to the rear, ejecting the fired cases. The cylinder is now ready to be reloaded.

In break-top revolvers, the frame is hinged at the rear such that, on release of a top catch, the barrel and cylinder swing down, exposing the back of the cylinder for loading (Figure 1.2b). The opening action will also eject empty cases from the cylinder. This form of weapon is relatively uncommon in the United States, but was the traditional form of revolver in Great Britain. This design is essentially obsolete.

Figure 1.2 (a) A revolver, swing-out type, with cylinder swung open exposing chambers. (b) Break-top revolver with action open. (Photo courtesy of Randall Frost, MD.)

Figure 1.3 Solid-frame revolver with loading gate swung open. Arrow points to loading port where individual cartridges are inserted.

The solid-frame revolver is the oldest form of revolver, dating back to Colt’s original weapons (Figure 1.3). In this weapon, the cylinder is held in the frame by a central pin, around which it rotates. The back of this cylinder is never exposed completely by either swinging out or breaking open. Each chamber in the cylinder is loaded individually through a loading gate on the right side of the frame. The hammer of the weapon is typically pulled back to half-cock, and the cylinder is then manually rotated so that a chamber is aligned with the loading gate. A cartridge is inserted. The cylinder is then manually rotated to the next chamber, and a second cartridge is inserted. This procedure is continued until the cylinder is completely filled. After the weapon is discharged, the cylinder has to be manually rotated again and aligned with the loading gate, and each cartridge is ejected through the gate using the ejector rod. This type of construction is most commonly encountered in single-action revolvers and the early model Saturday night specials. The latter term, dating back to the early twentieth century, refers to a cheap weapon usually of poor construction and does not refer to concealability.

Revolvers may be either single-action or double-action types. In single-action revolvers, the hammer must be cocked manually each time the weapon is to be fired. Cocking the hammer revolves the cylinder, aligning the chamber with the barrel and the firing pin. Pressure applied to the trigger then releases the hammer, discharging the weapon. In double-action revolvers, a continuous pressure on the trigger revolves the cylinder, aligns the chamber with the barrel, and cocks and then releases the hammer, firing the weapon. Most double-action revolvers may also be fired in the single-action mode. The amount of pressure on a trigger necessary to fire a well-made double-action revolver varies from 12 to 15 lb. If these weapons are cocked and fired in single-action mode, less pressure (2–4 lb) is necessary to fire them. The double-action trigger pull for cheap, poorly made revolvers is usually much greater, while single-action trigger pull may vary from less than a pound to as much as the double-action pull in a well-made revolver.

Single-action revolvers may have a “half-cock” notch in the cocking hammer that lies between the position of “full cock” and “fired.” The purpose of the half-cock notch is to catch the hammer if it accidentally slips from the thumb as it is being manually cocked. Many individuals incorrectly consider the half-cock notch a safety position and will carry weapons on “half-cock.” Dropping a weapon when on half-cock may cause the hammer to disengage, fly forward, and discharge the weapon. Some single-action revolvers will fire from the half-cock position if the trigger is pulled. Ruger single-action revolvers equipped with a safety bar do not have a half-cock notch.

The cylinder of a revolver may rotate either clockwise (Colt revolvers) or counterclockwise (Smith & Wesson revolvers). This difference has resulted in a number of deaths among individuals playing Russian roulette, in which an individual loads one chamber of a revolver and spins the cylinder. They then peek to locate the cartridge. If it is in any cylinder except the one that will be rotated into firing position on pulling the trigger, the gun is then put to the head and the trigger pulled. If the cartridge is in the lethal chamber, the player makes some excuse to spin the cylinder again. This system of playing Russian roulette is theoretically safe if one knows which way the cylinder rotates. A person familiar with playing the game using a Colt revolver may try it with a Smith & Wesson revolver in which the cylinder rotates in the opposite direction and may experience a fatal conclusion to the game.

Autoloading Pistols (Automatics)

Autoloading or automatic pistols make up the fourth category of handguns. The term “automatic pistol” is a misnomer, as this form of pistol is an autoloader in which the trigger must be pulled for every shot fired. Regardless of the correct terminology, however, these weapons are invariably called “automatics” or just “pistols.” These pistols use the forces generated by the fired cartridge to operate the mechanism that extracts and ejects the empty cases, loads the fresh cartridge, and returns the mechanism into position to fire the next round (Figure 1.4). The first commercial automatic pistol was produced in 1893 by Borchardt; this weapon was the predecessor of the Luger.

The cartridges are almost invariably stored in a removable magazine in the grip of the pistol. Some automatic pistols, such as the Intratec Tec-9 and the Mauser M1896, have the magazine in front of the trigger guard. The Calico Auto Pistol uses a 50- or 100-round helical-feed magazine on the top rear of the frame. The term “clip” is often used synonymously with the term “magazine.” In fact, a clip is a device designed to facilitate the loading of a number of cartridges into a magazine. Most people, however, use the terms interchangeably.

Figure 1.4 The weapon has just been fired. The slide has begun to recoil with the bullet a few inches in front of the muzzle. The fired cartridge case is being ejected and the gun cocked. The slide will come forward, chambering a new round.

Figure 1.5 Heckler-Koch P7 9 mm pistol with squeeze cocker constituting front portion of grip. (Retrieved from Wikipedia Commons 10/15/2014. Photo released into the public domain by user and author Michael Sullivan, original upload date October 30, 2009.)

There are five methods of operation of automatic pistols: blow back, delayed or retarded blow back, blow forward, recoil, and gas. Only two of these methods are currently in widespread use: blow back and recoil.

In a blow-back action, the pressure of the gas produced by combustion of the powder forces an unlocked slide to the rear, thus starting the cycle of extraction, ejection, and reloading. The Heckler and Koch P7 pistol is blow back operated with a recoil breaking system that delays breech opening (Figure 1.5). On firing the gun, part of the propellant gas is directed through a small vent in the barrel ahead of the chamber into a cylinder beneath the barrel. A piston attached to the slide enters the front end of this cylinder. The gas entering the cylinder acts against the piston, such that as the slide begins to move rearward by virtue of the recoil pressure, the movement of the piston in the cylinder is resisted by the gas pressure, delaying the movement of the slide and delaying the opening of the breech. Another unusual feature of this weapon is that the firing pin is cocked by a squeeze cocker incorporated in the front of the grip (Figure 1.5). On grasping the grip, the fingers depress the squeeze cocker, automatically cocking the gun. If the pressure on the grip is released, the squeeze cocker goes forward uncocking the gun. P7 pistols have fluted firing chambers and polygonal rifling of the barrels (see Chapter 2). By virtue of its construction and design, the HK P7 was extremely expensive to manufacture. Its accuracy and reliability, however, makes it a favorite weapon of special police and military units in Europe.

In a recoil-operated automatic pistol, the barrel and the slide are locked together at the moment of firing. As the bullet leaves the barrel, the rearward thrust of the propellant gas on the cartridge case starts the barrel and slide moving to the rear. After a short distance, the barrel is halted, and the locking device is withdrawn from the slide (Figure 1.6). The slide then continues to the rear, eje...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Dedication
• Table of Contents
• Foreword
• Acknowledgments
• Editor’s Note
• 1 Firearms and Ammunition
• 2 Forensic Aspects of Ballistics
• 3 Wound Ballistics
• 4 Introduction to the Classification of Gunshot Wounds
• 5 Wounds due to Handguns
• 6 Wounds from Rimfire Firearms
• 7 Wounds from Centerfire Rifles
• 8 Wounds from Shotguns
• 9 Bloody Bodies and Bloody Scenes
• 10 Weapons and Ammunition: Miscellaneous
• 11 X-Rays
• 12 Detection of Gunshot Residues
• 13 Correct Handling of Deaths from Firearms
• 14 Suicide by Firearms
• Appendix A: Stopping Power and Hollow-Point Pistol Ammunition
• Appendix B: Forensic Autopsy in Gunshot Wound Cases
• Index