Rifled Weapons

INTRODUCTION

This blog article is a synopsis of our latest Forensic Science Newsletter ‘Rifled Weapons.’

Rifled weapons include handguns, pistols and revolvers, and rifles.  These are weapons in which spiral grooves have been cut into the length of the interior or bore of the barrel (Fig. 1).  Rifling consist of ‘lands’ and ‘grooves’ (Fig. 2).  The ‘lands’ grip the bullet as it passes down the barrel, giving the bullet a rotation, which has a gyroscopic effect that increases the stability of the bullet’s trajectory and thus its accuracy (Fig. 3).  In contradistinction to rifled weapons, shotguns are smooth bored.  This is because rifling in a shotgun barrel would cause the shot to disperse to quickly in a 360 degree arc.

GENERAL INFORMATION

Handguns and rifles are breech-loading firearms in which the cartridge is inserted or loaded into a chamber, which is integral to the rear portion of the barrel.  The breech or chamber has a slightly greater diameter than the rest of the barrel.  The missile fits snugly into the breech-chamber, but is too large to pass through the barrel being squeezed.  The barrel is grooved in a spiral fashion from the breech-chamber to the muzzle, with the friction between the squeezed missile and the ridges between the grooves (lands) imparting to the missile a spinning motion.

Handguns include the single-shot pistols, Derringers, revolvers and auto-loading pistols (automatics) (Figs. 4-7).  There are two types of revolvers, single-action and double-action.  Automatic pistols (semiautomatic handguns) are divided into three categories: single-action, traditional double-action or double-action only (Figs. 8-10).

Rifles are firearms designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves (“rifling”) cut into the barrel walls.  The word “rifle” originally referred to this grooving, and a rifle was called a “rifled gun.”  This rifling, as discussed above, implants a spin to the fired missile, impacting a spin around an axis corresponding to the orientation of the weapon.  Once the missile leaves the barrel, this spin lends gyroscopic stability to the projectile and prevents tumbling (Fig. 3).  This allows the use of aerodynamically efficient bullets, as opposed to the spherical balls used in muskets, which improves range and accuracy.  This spin also contributes to the total kinetic energy released by the missile on its penetration of the target. Rifles are divided into single-shot, lever-shot, bolt-action, pump-action, and autoloading or semiautomatic rifles and automatic rifles (Figs. 11-21).

CALIBER

The caliber of a rifle or handgun, is either the internal diameter of the bore of the barrel before the rifling grooves were cut, measuring from ‘land’ to ‘land’ (Fig. 2) or the diameter of the bullet.  Common caliber designations are given in either the English system in hundredths of an inch, I.e., .22, .38, .45 or in the metric system in millimeters, I.e., 7.42 or 9 mm.  Thus, a .22-caliber gun fires a .22-caliber bullet.

In the autopsy reports of forensic pathologists, they often describe bullets as small (.22, .25), medium (.32, .38, and 9 mm), or large (.40, .45, .50) caliber, which is based on the measurement of the bullet’s diameter.

It is important to understand, the caliber designation as used in the United States can be confusing for it is neither accurate or consistent.  For example, the .303 Savage fires a .308-inch-diameter bullet.  The .303 British cartridge has a 0.312-inch-diameter bullet.  Both the .30-06 and the .308 Winchester cartridges are loaded with bullets having a diameter of 0.308 inches.

The European system of cartridge designation, which uses the metric system, is more thorough and logical than the US system.  It identifies a cartridge by giving the bullet diameter and the case length in millimeters, as well as designating the type of cartridge case.  Thus, the Russian rimmed service round becomes the 7.62 x 54 mmR.  The 7.62 refers to the diameter of the bullet; 54 mm indicates the length of the cartridge case and R indicates the round is rimmed (Fig. 22).

ANOTHER FORM OF IDENTIFICATION OF BULLETS

Bullets can also be identified by whether they are jacketed (Figs. 23-25).

WOUND  BALLISTICS

The total kinetic energy of a bullet is due to two factors: Rotational or angular kinetic energy and the energy due to linear or translational motion.

Effects of Alcohol on Traumatic Brain Injuries and Second Impact Syndrome

Traumatic brain injury scanINTRODUCTION

When a Forensic Pathologist and/or Neuropathologist evaluates a brain that has been subjected to traumatic brain injury (TBI), they tend to focus on the anatomic injuries, i.e., fractures of the calvarium or base of the skull; presents of epidural, subdural or subarachnoid hemorrhage; acute contusions, whether they be coup, contracoup or gliding; the presence of intraparenchymal hemorrhage; the presence of edema; and evidence of herniation to name a few of the anatomic injuries.

Continue reading Effects of Alcohol on Traumatic Brain Injuries and Second Impact Syndrome

Postmortem Hemorrhage: Examination by a Forensic Pathologist

Forensic Science Newsletter: February 2017

A recent case I was asked to review involved a victim who had been shot multiple times.  In the first two trials the jury was unable to reach a verdict whether the shooting of the victim was self defense or murder.  The prosecution decided to try the shooter a third time.  As a forensic pathologist, I was subsequently asked to review some of the trial testimony, police reports, autopsy reports and the scene and autopsy photographs.

In the autopsy, the Forensic Pathologist states there was 750 cc of blood in the right pleural cavity; 450 cc in the left pleural cavity; 30 cc in the pericardial sac; and 100 cc in the abdominal cavity.  At the time of the trials, the Prosecutor inquired of the Forensic Pathologist, the significance of the blood in the respective cavities and the pericardial sac.  Continue reading Postmortem Hemorrhage: Examination by a Forensic Pathologist

Injuries to the Vertebral Column and Spinal Cord: A Summary

Spinal Cord Injury: Forensic NeuropathologyThis article is a brief summary of the 19 page article entitled “Traumatic Spinal Cord Injuries,” published as a Forensic Science Newsletter on January 15, 2017.

General Information

The earliest known reference to traumatic lesions of the spinal cord are found in the Edwin Smith Surgical Papyrus.  During World War I, Riddoch, and later Head and Riddoch, gave what are now considered the classic descriptions of spinal transection in humans.  World War II marked the turning point in the understanding and management of spinal injuries. Continue reading Injuries to the Vertebral Column and Spinal Cord: A Summary

Traumatic Spinal Cord Injuries

Spine Injury Forensic X-RayForensic Science Newsletter: January 2017

Neuropathology

In this Forensic Science Newsletter we will discuss traumatic spinal cord injuries.

Traumatic lesions of the spinal cord usually result from injuries which cause vertebral fractures.  The spinal cord may, however, be injured by vertebral dislocation without fracture or by penetrating wounds of the canal.

The common sites of injury are at levels of the upper cervical, the mid cervical, the lower cervical, the lower thoracic, and the upper lumbar vertebrae.  In approximately three-fourths of the cases of fracture of the cervical vertebrae, the spinal cord is injured.  Slightly more than half of the fractures of the thoracic spine and only about one-fourth of the fractures of the lumbar spine were associated with spinal cord injury.

Continue reading Traumatic Spinal Cord Injuries

Subconcussive Head Trauma

Neuropathology

In this Forensic Science Newsletter we will discuss subconcussive head trauma, its definition, general information, clinical presentation, pathophysiology and biomarkers.

Definition

Subconcussive head trauma is head trauma that does not result in recognized concussion symptoms or signs.  It is due to blows to the head, which are below the threshold to cause or elicit any symptoms or sign of a concussion.

Read the full newsletter to learn more about Subconcussive Head Trauma.

Second Impact Syndrome: A Medical Catastrophe that need not occur

In our most recent Newsletter, “Second Impact Syndrome,” is discussed at length. You can also sign up here to receive our Forensic Science Newsletter by email.

Definition of Second Impact Syndrome (SIS)

Occurs when an athlete who has sustained a mild traumatic brain injury, usually a concussion, with or without loss of consciousness, suffers a second traumatic brain injury before the symptoms associated with the first have cleared. Such patients are at risk for developing intense cerebral vascular congestion followed by diffuse brain swelling, which typically occurs immediately after the second impact to the head or to the trunk, the latter imparting acceleration to the brain.

Concussion is defined as a trauma-induced alteration in mental status, usually characterized by confusion and amnesia that may or may not involve loss of consciousness, link “Mild Traumatic Brain Injury (Concussion) in Infants, Toddlers, Children and Adolescents.” Continue reading Second Impact Syndrome: A Medical Catastrophe that need not occur

Does Post-Concussion Syndrome Commonly Occur in Children

In the highly regarded Neurology Textbook, “Principles of Neurology,” by Adams and Victor, tenth edition, it is stated post-concussion syndrome is virtually unknown in children. However, a careful search of the scientific neuropathology literature suggest otherwise.

In our latest Newsletter, “Post-Concussion Syndrome-Children” an in depth discussion of this issue is presented. You can also sign up here to receive our Forensic ScienceNewsletter by email.

Definition of Post-concussion syndrome (PCS)

A name given to symptoms that develop following a concussion, which persist for an extended time. Most concussions in children resolve in 7-10 days.

General Information

Most children and adolescent athletes return to their normal activities within two weeks. Those who develop post-concussion syndrome have symptoms, such as tiredness, headache, memory loss, dizziness, irritability, poor attention, depression, difficulty in concentration, sleep problems, and personality changes that last for at least one month. Continue reading Does Post-Concussion Syndrome Commonly Occur in Children

The Quanundrum of Post-Concussion Syndrome

X-Ray Concussion of the BrainAlthough there is much confusion in the literature regarding what is post-concussion syndrome, a picture is beginning to emerge, which provides clarity as to our understanding of its seemingly confusing presentation.

In our latest Newsletter, “Post-Concussion Syndrome-Adults,” we present a comprehensive analysis of this subject.  The following blog article is meant only to touch on some of the aspects of this complex subject.  You can also sign up here to receive our Forensic Science Newsletter by email.

Continue reading The Quanundrum of Post-Concussion Syndrome

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