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Firearms are a deadly efficient weapon and are commonly used to harm by individuals to harm others. Even with Australia's relatively strict gun laws there is still a significantly high number of crimes involving firearms which therefore requires a forensic team to have a good knowledge in firearm analysis and identification. In a firearm related crime the complete identification of a firearm often requires the forensic officer involved to determine the make or manufacture, type, caliber or gauge, serial number, model, barrel length and number of shots it has the capacity to fire. They must also be able to determine the distance at which the weapon was fired (range) and analyze primer and gunpowder residue deposits in order the identify and convict suspects.
The most common task of a firearm examiner is to link a bullet back to the weapon it was fired from. .
The class characteristics of a firearm are the features that identify the make and model. These characteristics must be determined to link a bullet back to what it was fired from. The barrel of a firearm is manufactured by a step know as rifling (Rowe, 2000). This involves impressing its inner surface with spiral grooves. The original surfaces, or bore, between the grooves is referred to, as lands and they are at equal distance apart. The diameter between the lands of the barrel is the called the firearms caliber. Different makes and models of firearms will have different caliber's, different directions of twists in the groove and a different number of lands and grooves. For example, Marlin rifles are rifled by a unique process called microgrooving resulting in 8 to 24 grooves impressed into their barrels. As a bullet is made slightly oversized for the barrel in which it is to be fired out of it will bare an imprint of the number of lands and grooves of the barrel and the direction and degree of the twist of the grooves (Rowe, 2000).