Saturday, December 3, 2011

Ballistics in Forensics - What Are Rifling Patterns on a Bullet?

!±8± Ballistics in Forensics - What Are Rifling Patterns on a Bullet?

When a bullet is fired from a gun, the gun leaves unique markings, or grooves, on the surface of the bullet as it travels through the barrel. These grooves help forensic firearms examiners determine a match between the bullet and gun type and perhaps to the actual gun used in a crime.

What is a Rifling Pattern?

A spinning bullet is a more accurate bullet. Therefore, many guns have spiral grooves carved into the inside of their barrels to make the bullets spin as they leave the gun barrel. The procedure for carving grooves into the barrel of a gun is called rifling. Cutting the grooves leaves high parts, or lands, intact between them. The grooves grab the bullet as it traverses the barrel and cause it to spin and thereby increasing its accuracy of hitting the intended target. Old smoothebore rifles were not accurate beyond 100 feet or more, but present day rifled firearms are highly accurate to several thousands of yards.

Accuracy is not at the top of the list of the Calleigh Duquesnes (a character on CSI: Miami) of forensic firearms examiners. Their interest is how the lands and grooves of the rifling procedure mark the bullet.

When a gun barrel is manufactured, the rifling is etched inside of it. The depth of the grooves, the width of the lands, and the degree and direction of the spiral vary among different types of firearms and different manufacturers. These qualities help forensic examiners identify the type of gun that fired a bullet found at the crime scene and its manufacturer.

As an example, let us say a .32 caliber Smith & Wesson handgun has five lands and grooves with a right hand (clockwise) twist, and .32 caliber Colt has six lands and grooves with a left hand (counterclockwise) twist. Browning firearms also have six grooves, but have a clockwise twist. Marlin rifles utilize a method known as microgrooving. Microgrooving leaves between 8 and 24 narrow grooves within the barrel. Suppose a firearms examiner is given a .32 caliber bullet taken from an autopsy, and he discovers grooves compatible with a bullet having traveled down a barrel with five lands and a clockwise twist, the murder weapon was likely a Smith & Wesson, and forensic investigators can exclude all other handgun types and target .32 caliber Smith & Wesson handguns.

To make the firearms examiner's job easier, the Federal Bureau of Investigation (FBI) keeps a database known as the General Rifling Characteristics file to assist with making their determinations. It delineates the land, grooves, and twist qualities unique to known firearms. Similarly, bullet and shell casings can be matched with bullets and casings taken from other crime scenes that are listed in other databases.

Because smoothbore firearms like shotguns and older model firearms are not rifled, their bullets will not show any evidence of marking caused by lands, grooves, or twists. This makes the forensic firearms examiner's job a lot harder.


Ballistics in Forensics - What Are Rifling Patterns on a Bullet?

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Monday, November 28, 2011

Civil War Weapons - Overview

!±8± Civil War Weapons - Overview

Whether you had ancestors that fought for the North or the South, almost every American is in some way tied to the history of the Civil War. Each of the weapons used in the Civil War has its own history as well. And owning an original relic is very expensive and not for every collector. But there are several companies building quality replica Civil War rifles and handguns that anyone can own for a reasonable price. There isn't much better conversation piece than a Griswold and Gunnison hanging in your office or in your home.

The British Enfield was similar to the Springfield and was used by both the Union and Confederate troops. Soldiers could use the same caliber ammunition in the British Enfield as with the Springfield. But the Enfields weren't machine made like the Springfields, and many units did what they could to exchange Enfields for Springfields.

The Austrian Lorenz was another widely used European rifle, used by both Union and Confederate troops. Some smooth-bore muskets like the 1842 Springfield were used frequently too, but against enemies armed with rifles, they were not very effective.

The short barreled carbine was the shoulder weapon of choice for cavalry units, and it was effective to 200 yards. Some 20 different types were used by Union forces. Cavalry on both sides used Sharps, which were 0.52 caliber arms. They were widely used by Gen. John Buford's division when they pushed back the Confederates' advance towards Gettysburg in July 1853. These were single shot weapons but could be loaded easily enough that a troop could fire five shots a minute versus three from muzzle-loading muskets.

The Confederates made their own Sharps copies, but they were not very useful because only 5,000 were ever made and many were defective, according to accounts by Gen. Robert E. Lee. Instead, many Confederates on horseback used captured Yankee breach-loaded weapons or short-barreled muzzle loaders.

The Union forces used.52 caliber Spencers that were patented in 1860 that could fire off seven shots in half a minute. This frequency of fire overwhelmed Confederates using their slower muzzle-loading muskets. The.44 caliber Henry Rifle was another well-liked repeater that put the Confederates at a clear disadvantage. Even if the Confederates had got their hands on these weapons, they would have had to produce special cartridges, which they could not have done.

The Yankees and Confederates were more equally matched when it came to handguns, particularly those made by Samuel Colt. While most Samuel Colt revolvers went to Union troops, the Confederates had stocked up on them prior to the firing on Fort Sumter. Colt's Navy.36 caliber revolver was also widely available to the Confederates, and was a preferred weapon of horsemen. Remington and Sons supplied Union troops with revolvers that had simplified designs and a solid frame, making them both stronger and cheaper to build than the Colt. After the war, Union troops were given the option of purchasing their sidearms, and more of them chose Remingtons than Colts.

Smith and Wesson made.22 and.32 caliber revolvers during the war, but in small quantities. Most were purchased privately. Lefaucheux revolvers made in France were used by Union troops in Western battles, while the Confederates bought thousands of five shot Kerr revolvers.

When it came to manufacturing Civil War weapons, Southerners were at a great disadvantage due to lack of raw materials necessary for building the weapons. Sometimes church bells were melted down to supply the materials for making arms. Griswold and Gunnison was the most productive maker of Confederate revolvers, making.36 caliber brass framed Navy copies. A weapons maker called Spiller and Burr made.36 caliber revolvers in Atlanta and then Macon, but the pace of production was too slow to keep up with demand.

The single shot musket was the infantry soldier's basic weapon during the Civil War. The one made by Springfield in Massachusetts was the most common. This musket had a 39-inch long barrel and could hit targets 500 yards away effectively. The Confederates started making their own copies of Springfields after the raid on Harper's Ferry, Virginia.

For more information about the history of Civil war weapons visit the Smithsonian Institute interactive website. Their website has excellent descriptions of the original weapons as well as high quality images of each. Or for great looking replicas of some of these historical pieces, you can visit us at Civil War Classics.


Civil War Weapons - Overview

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