Deck 13: Firearms and Firearms Discharge Residue

Question 1

The energy that is transferred to a bullet as kinetic energy comes from

A) chemical energy in the propellant
B) mechanical energy from the primer
C) friction heat from the barrel
D) the firing pin striking the primer
E) none of the above

Answer 1

A

Question 2

The purpose of the lands and grooves in a firearm is to

A) control the burn rate of the propellant
B) conver hot expanding gas into PV work
C) clear the barrel of debris
D) impart spin to the bullet
E) none of the above

Answer 2

D

Question 3

The primer in an ammunition cartride

A) is designed to scavange degradation products from nitrocellulose
B) contains a shock-senstive explosive
C) provides the hot expanding gases that drive the bullet from the barrel
D) is designed to be insensitive to prevent misfires
E) none of the above

Answer 3

B

Question 4

The two primary energetics in double-based propellant are

A) diphenylamine and nitroglycerin
B) lead styphanate and diphenylamine
C) nitrocellulose and nitroglycerin
D) ethyl centralite and lead styphanate
E) none of the above

Question 5

Green primer formulations

A) contain barium, lead, and antimony
B) do not contain lead
C) are named because of the color of the smoke
D) do not contain explosives
E) none of the above

Question 6

The burn rate of propellants is controlled to

A) optimize the rat of production of hot expanding gases
B) prevent backfires
C) ensure the cartridge case can be ejected
D) drive the slide back in semi-automatic pistols
E) none of the above

Question 7

Given the following information regarding a typical cartridge of 9mm ammunition: $$\begin{array} { | r | l | l | } \hline 1 \text { gram } & 15.43 & \text { grains } \\\hline \text { Propellant energy } & 4545 & \mathrm {~J} / \mathrm { g } \\\hline \text { Mass of propellant } & 5.7 & \text { grains } \\\hline \text { Efficiency } & 59 \% & \\\hline \text { Bullet weight } & 115 & \text { grains } \\\hline\end{array}$$ Calculate the mass of the bullet in grams

A) 10.0
B) 13.4
C) 7.5
D) 8.3
E) none of the above

Question 8

Given the following information regarding a typical cartridge of 9mm ammunition:
$$\begin{array} { | l | l | l | } \hline 1 \text { gram: } & 15.43 & \text { grains } \\\hline 1 \mathrm { oz } & 28.35 & \mathrm {~g} \\\hline \text { Propellant energy: } & 4545 & \mathrm {~J} / \mathrm { g } \\\hline \text { Mass of propellant } & 5.7 & \text { grains } \\\hline \text { Efficiency } & 59 \% & \\\hline \text { Bullet weight } & 115 & \text { grains } \\\hline\end{array}$$
Calculate how much chemical energy from the propellant will be available to impart to the kinetic energy of the bullet. Report in J

A) 149
B) 46
C) 2862
D) 991
E) none of the above

Question 9

Given the following information regarding a typical cartridge of 9mm ammunition:
$$\begin{array} { | l | l | l | } \hline 1 \text { gram: } & 15.43 & \text { grains } \\\hline 1 \mathrm { oz } & 28.35 & \mathrm {~g} \\\hline \text { Propellant energy: } & 4545 & \mathrm {~J} / \mathrm { g } \\\hline \text { Mass of propellant } & 5.7 & \text { grains } \\\hline \text { Efficiency } & 59 \% & \\\hline \text { Bullet weight } & 115 & \text { grains } \\\hline\end{array}$$
Calculate the muzzle velocity in m/s. 1J = 1 (kg m²)/s²

A) 516
B) 628
C) 722
D) 910
E) none of the above

Question 10

What is the primary purpose of stabilizers in propellant? To

A) keep the nitroglycerin in liquid form
B) prevent the primer from degrading
C) capture breakdown products from nitrocellulose
D) prevent autoignition of the propellant
E) none of the above

Question 11

Color tests are used in firearms testing for what purpose?

A) to screen hand samples for lead
B) to estimate distances from muzzle to target
C) to screen stubs for GSR
D) to test nasal swabs for GSR
E) none of the above

Question 12

What characteristics are used to characterize particulates as GSR?

A) size, numbers, and elemental composition
B) size, shape and elemental composition
C) shape, elemental composition, and reaction with color test reagents
D) size, shape, and brightness under SEM conditions
E) none of the above

Question 13

Why are GSR particulates smooth?

A) They form by condensation
B) The firing process violently removes any surface features
C) Lead and barium form alloys
D) They are hollow
E) none of the above

Question 14

Particulates described as "characteristic of" GSR contain which 3 elements?

A) Pb, Sb, and Ba
B) Al, Pb, and Sb
C) Ca, K, and Ba
D) Ba, Al, and Ti
E) none of the above

Question 15

All of the following are potential sources of false positives in GSR analysis except

A) airbags
B) fertilzer
C) welding
D) all are potential sources

Question 16

Serial number restoration in metals is based on

A) attempting to visualize markings made in the regions deformed by stamping
B) Raman spectroscopy
C) color tests
D) SEM imaging
E) none of the above

Question 17

Chemical etching is based on what type of chemical reaction?

A) proton affinity
B) partitioning
C) diffusion
D) oxidation/reduction
E) none of the above