Identification of fired cartridges by means of chamber marks is well known.The present paper deals with the existence and utility of unusual chamber marks which are often present on the bottle-necked cartridges fired through locally made firearms,but generally overlooked. These marks serve as an additional means for identifying fired cartridges.
Locally made firearms are manufactured crudely and do not conform to standard specifications. Their chamber shape and size therefore vary considerably. The shoulder gradient in the chamber for accommodating bottle necked cartridges is not correctly made. The shoulder formation and the leed are also often missing. The chamber and the bore are connected crudely and the surface at the joint is often very rough and irregular.
Cartridges fired throug such firearms will develop characteristic shoulder necks. The position of the shoulder neck junction of the fired cartridge will, however depend upon the position of the chamber-bore joint of the firearm and it may or may not coincide with the original shoulder neck junction of the unfired cartridge.( Fig1)
The surface irregularities of the chamber- bore junction are imprinted all around the circumference of the fired cartridge. Unlike normal chamber marks, these marks are often not visible as such, and are generally overlooked. They require special attention and often adequate magnification for detection and evaluation.The arrow marks in FIG 1 indicates the actual position where these unusual chamber marks are developed.
In a murder case, the fired cartridge cases had blown caps, and no other significant characteristic marks of breech face, extractor, chamber, etc.were present which could allow positive identification. The presence of characteristic unusual chamber marks of the chamber bore joint on the test cartridges led to definite positive conclusion. FIG 2 and FIG3
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It has been observed that locally made firearms meant for firing bottle-necked cartridges often imprint characteristic unusual chamber marks on the shoulder neck junction of the fired cartridges, which can independently lead to a definite conclusion. They are of great importance in the absence of any other evidence.
Return to Cartridge Identification
Cartridge Identification by Chamber Marks without test firing
Test extractor marks under low pressure on Shotgun Cartridges
Deceptive striations on fired cartridges
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