Eastern Florida State CollegeSCIENCE BSCC-1010Kami Export - RAEANN UBINAS - bullet_striations_training_lab

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TRAINING LAB – FIREARMS AND BALLISTICS: BARREL AND BULLET STRIATIONS NAME___________________________________________ Background: You have learned that the inside of a firearm’s barrel contains ... lands and grooves in a twisting pattern, which forces an exiting bullet to spin. The pattern of lands and grooves can help you determine the manufacturer of a firearm – an example of Class Evidence. You may also recall that many small scratches or STRIATIONS are left behind in a firearm’s barrel during the process of manufacturing the lands and grooves – and that each firearm has its own unique set of striation “fingerprints”. This is an example of Individual Evidence. In this Training Lab you will continue your study of BALLISTICS (the study of firearms and the bullets they fire) and investigate barrel and bullet striations in more detail. 1. You will be trained to analyze the striation patterns on evidence bullets and use this information to help solve a crime. Procedures: 1. The striations in a firearm’s barrel are just like fingerprints – each with it’s own unique pattern of striations. When a bullet is fired it rubs against the inside of the firearm’s barrel and picks up an imprint of the barrel’s unique striations. Find a bullet at a crime scene and you can use the bullet’s striation marks to identify the gun that fired it. 2. You need two things to identify a gun that fired a bullet at a crime scene: A. You need an evidence bullet that has visible striation marks. This can be a problem because many times the bullet is destroyed when it hits an object – fragmenting into many pieces or being smashed in a way that destroys the striations. However, you can still match an evidence bullet to a gun if only a portion of the evidence bullet contains striation marks. B. You need the firearm that you think may have fired the bullet. It is difficult to actually check the striations inside a gun’s barrel to compare them to an evidence bullet’s striations. It’s much easier to fire another bullet from the suspect gun and compare the striations on this known bullet to the striations on the evidence bullet to see if they match. The known bullet is usually shot into a large tank of water where it can be collected without any damage. 3. Now, let’s put your ballistic skills to work and solve the following crime [Show More]

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