Question

exit slip: how do ballistics experts match a bullet to a gun?

Explanation:

Ballistics experts match a bullet to a gun mainly by examining the striations (microscopic grooves) on the bullet. When a bullet is fired, the gun's barrel (with its unique rifling pattern) imparts these striations. They use comparison microscopes to compare the striations on the recovered bullet with those from test - fired bullets from a suspect gun. Also, the caliber (diameter) of the bullet, the type of ammunition, and the firing pin impressions (for rimfire or centerfire guns) can be used. The rifling pattern (number of lands and grooves, their direction and twist rate) is unique to a gun's manufacturing and wear, helping in the matching process.

Answer:

Ballistics experts match a bullet to a gun by examining striations (from the gun's rifling) with a comparison microscope, checking caliber, ammunition type, firing pin impressions, and rifling pattern (lands/grooves, direction, twist rate).