Straight up firearm tools

NIBIN (National Integrated Ballistic Information Network)

• It:

  • Captures images of fired cartridge cases

  • Extracts a ballistic “signature”

  • Compares it to a database of other shootings

• Helps link crimes involving the same firearm

primary concern of firearm identification

To determine if:

• A bullet or cartridge case was fired from a specific firearm

Comparison microscope

• Two microscopes joined together

• Lets examiner compare evidence vs test sample side-by-side

components of a cartridge

• cartridge car

• primer

• gunpowder

• bullet

cartridge case

holds everything p

primer

ignition- contains lead styphnate, barium and antimony

types of gunpowder

smokeless, and black powder

smokeless gunpowder

nitrocellulose, cleaner and faster

blackpowder gunpowder

older, smoky and unstable

bullet

projectile

primer ingredients

lead styphnate, barium, antimony

smokeless powder ingreident

nitrocellulose

full metal jacket

penetration, less deformation

hollow point

expands- more tissue damage

soft point

partial expansion

wadcutter

clean holes; target shooting

frangible

breaks apart; less ricochet

armor piercings

penetrates hard targets

Desirable Wounding Components (Handgun Ammo)

• Penetration

• Expansion

• Energy transfer

• Controlled deformation

Firearm mechanics; action types

• boltaction

• semi automatic

• single action

• double action

• pump action

• lever action

• fullo auto

bolt action

manuel bolt

semi automatic

fire ones round per trigger pull, auto reloads

single action

trigger performs one action, release hammer

double action

trigger cocks and releases hammer pump

pump action

manual sliding mechanism

lever action

lever reload

full auto

continuous fire while trigger held

revolver

uses cylinder

• holder multiple founds

  • cartridge stays in cylinder

semi auto

uses magazine

• ejects spent cartridge cases

• automatically reloads next round

what is rifling

• spiral grooves inside barrel

• causes bullet to spin- stability

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types of rifling

conventional and polygonal

conventional

sharp lands and grooves

polygonal

rounded and smoother interior

rifling terms

lands and grooves

lands

raised areas

grooves

cut areas

caliber

diameter of bullet/barrel

recoil

backward force when firing

trajectory

curved path of a projectile

fracture match

matching broken pieces to prove they were once one subject

class characteristics

• general features (caliber, rifling pattern)

  • shared by a group

individual characteristics

• unique microscopic marks

• causes by wear, damage, manufacturing imperfections

distance determination

based on gunshot residue (GSR) patterns s

stippling (tattooing)

unburned powder hitting skin

closer distance

there is more residue left

sodium rhodizonate

tests lead

modified griess

tests nitrites

SEM-EDX

tests elemental analysis

other types of examiner tests

• test firing

• rigger pull measurement

• shock/drop test (accidental discharge)

• GSR analysis

types of tool marks

• Striations – sliding motion (scratches)

• Impressions – direct force (indentations)

• Can be a combination

strations

Contour variations, generally microscopic, on the surface of an object caused by a combination of

force and motion where the motion of the tool is approximately parallel to the plane being marked

impression

Contour variations on the surface of an object caused by a combination of force and motion where

the motion of the tool is approximately perpendicular to the plane being marked

serial number restoration

1. Polish surface

2. Apply techniques:

   • Chemical etching (different metal reactions)

   • Magnetic particle inspection

   • Electrochemical methods

Key Idea:

• Stamped numbers alter metal structure underneath

• Even if removed → can often be restored

university firearm safety

• Treat every gun as loaded

• Never point at anything you don’t intend to shoot

• Keep finger off trigger until ready

• Know your target and beyond

- Meaning of a firearm with 80% gun reference

• 80% = unfinished

• PMF = privately made

• Ghost gun = no serial number