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**Part of a chapter of
thesis-- Brief description**
Bullets fired from rifled
firearms (pistols,revolvers,rifles, etc) are engraved with the class
characteristic rifling marks - direction of rifling, width of lands and
grooves, depth of grooves, angle and pitch of rifling etc. The rifling
data of various make and model is well documented and is kept updated
by laboratory personnel. The data is helpful in ascertaining probable
make and model of the suspect firearm.It helps the investigator to lay
hands on probable firearms eliminating others. This procedure of
determining calibre, make and model of rifled firearms by class
characteristic rifling data is obviously not applicable to bullets
fired from mismatched rifled firearms. So also the data is not
applicable to bullets fired from non standard smooth bore illegal
firearms(home made,improvised or imitation firearms).In the absence of
usual class characteristic rifling marks,it is desirable to formulate
new parameters for evaluating type of non standard smooth
bore/mismatched rifled firearm from fired bullets.
Non standard smooth bore firearms designed to load and fire
pistol,revolver, rifle cartridges etc.
There is no pre-assigned spiral
path in non standard smooth bore firearms. The fired bullets do
not carry orderly barrel marks like those fired from standard rifled
firearms. Depending upon the constructional features of the smooth bore
barrel, the bullet makes contacts during its travel inside the bore. Examination
of barrel marks fired from various bullet-bore combinations revealed a
wide variation in class characteristic smooth bore barrel marks- deep
scoring around the periphery, superimposed striations etc. The study of
barrel marks coupled with plausible consideration of movement of the
bullet inside the smooth bore barrel has resulted into new
classification criteria for evaluating type of smooth bore firearm from
fired bullet. Significant barrel marks for evaluation are continuous
/discontinuous striae, parallel straight/inclined striae, striae in
patch/patches, insignificant striae,groove like engravings etc.
The nature of striae pattern identifies the following class characteristic parameters of non standard firearm :
i) BORE DIAMETER/SIZE
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