Firearms and Toolmarks Test # 2

Rim fire only survives as _______ caliber

.22

When were Berdan and Boxer primers invented?

1860's

Cartridge nomenclature

2.2.6

Pointed Bullet

A bullet with a long point that will hold its velocity and energy over a great distance

Rim fire

A flange-headed cartridge with the priming composition in the hollow rim

Boat Tail bullet base

A tapered rear end of the bullet, designed to decrease drag for long distance accuracy, usually greater than 200 yds

Why is black powder hard to use?

Absorbs atmospheric water, ignites easily by static electricity, and low impact ignition tolerances

------------- ----------- acts as a fuel to prolong burning time

Antimony Sulphide

Boxer Primer

Anvil is a small bent disc of steel INSIDE the cup making the primer completely self contained; centrally located flash hole

Flat Base

Base perpendicular to the sides of the bullet

Flat Bullet Base

Base perpendicular to the sides of the bullet

Tear Gas Cartridges

Blank ammunition containing lachrymatory/sternutatory substance either CN or CS gas

Obturation

Block up of the chamber; expanding and sealing of chamber during firing

Belted Cartridge Case

Cartridge case designed to provide positive headspacing and allow magazine feeding

Straight cased cartridges

Case diameter is approx the same along its length

Concave Bullet Base

Central Indentation

Concave Base

Central indentation

Early Black Powder contained _________.

Charcoal, sulfur and potassium nitrate

Berdan Primer designed by __________ _________ of the US Army Ordnance Department

Col Berdan

Boxer Primer developed by ____ ______ of the Laboratory at the Royal Woolwich Arsenal, England

Col Boxer

Compound Base

Combination of boat tail & recessed

Semi-rimmed Cartridge Case

Combination of rimmed and rimless design

Rebated Cartridge Case

Designed to allow a larger diameter case while using a smaller bolt face; e.g. .284 Winchester

What can you do to analyze a bullet with no lands and grooves?

Elemental analysis; can be matched to the ammunition in the possession of a suspect

Rimmed Cartridge Case

Flange larger than the diameter of the body of the cartridge case, holds the cartridge in place and stops the travel of the case into the chamber. Provides for easy extraction. Used mostly with revolvers.

Rimless Cartridge Case

Flange same size as diameter of the cartridge. Allows for smooth feeding from magazines

Internal Firing Pin Safety

Found in many semi-automatic pistols. When the trigger is forward a small internal plunger is blocking the pistol's firing pin. Pulling the trigger pushes the plunger up to unlock the firing pin

Where do you mark the weapon?

Frame, barrel, cylinder

________________ bullets are widely used to reduce target damage and prevent ricochet

Frangible

Spitzer

German term applied to an elongated pointed arch bullet with sharp point

Locked Breech Safety

Guns designed to fire from a closed and locked breech have block or interrupt safety

Boxer Centerfire

Has a single internal anvil, with one flash-hole. This allows convenient reload ability since the primer is easily punched out through the flash hole

Thermodynamic Energy

Heat is produced, for rapid burning and expanding gas

Ball Burnishing

High Quality Rifles; repeatedly pushing steel ball bearing of same size as the barrel lands through the bore

Expanding Nose Bullet Types

Hollow point; jacket cuts; thinning jacket near nose; using a double jacket; notching around jacket in a ring; hard metal wedge; slitting the jacket longitudinally; covering nose with aluminum

Interial (Floating) Firing Pin

Incorporates firing pin whose length is too short to span the distance between the forward most position of the hammer and the primer of a chambered cartridge and which is usually restrained in the rearmost position

-------- ------- is the sensitive explosive ingredient in primer

Lead Styphnate

Lead Fouling

Lead comes off the bullet in the barrel and may get blown out of the barrel

Twist Pitch

Number of inches of barrel for a complete turn of the bullet

____________ ammunition prevents lead fouling, reduces lead contamination, and reduce friction with the bore to enhance velocity.

Nyclad

Out of Favor Priming cartridges

Pinfire, lip fire, cup fire, teat fire

Berdan Primer

Primer cup contains only the priming mixture and the anvil is part of the cartridge case

Modern Smokeless Powder

Produces higher velocities, and produces less fouling of the barrel, with less smoke than Black Powder.

Heeled bullet base

Rear of the bullet is reduced so that the case diameter is the same as the driving surface; .22 caliber

How does hollow point bullets improve stability?

Removing material close to the axis shifts some of the mass out from the axis, increasing gyration

___________ cartridge case design depends on accurate case length

Rimless

____________ cartridge case designs are not well suited for use in box magazines

Rimmed

What are the three types of crimps?

Roll, Taper, Stabbed

Secondary Automatic Safety

Safety feature which requires no action on the part of the shooter to engage the disabling feature

What is the purpose of a crimp?

Securely and uniformly hold the bullet in the cartridge case

Recessed Base

Shallow, flat bottomed central indentation

Recessed Bullet Base

Shallow, flat-bottomed central indentation

What is the difference between "Boxer" and "Berdan" primers?

Size; internal construction; American vs European

Meplat

Small flat area on a pointed bullet to make it easier to handle and protect than a sharp point

Boat Tail Bullet Base

Tapered rear end of the bullet, designed to decrease drag for long distance accuracy, greater than 200 yds

______________ is a highly sensitive explosive chemical used in modern priming compounds

Tetrazine

Berdan Centerfire

The central anvil is part of the cartridge case. Usually two small flash holes on either side of the anvil. Not intended to be reloaded.

Foster Slugs

The defining characteristic of ____________ ______________ is the deep impression in the base; drag tends to push back into straight flight

Headspacing

The physical distance between the breach of the weapon and the design feature keeping the casing from going through the barrel

Burning Rate

The smaller the grain, the faster the burn; handguns require faster burning powder

How does hollow point bullet reduce stability?

Transfers the center of gravity further to the rear

Battery Cup

Used in the shotgun ammunition

Full Metal Jacket Bullet

Usually copper nickel alloy

Exposed Core Base

Visible lead core, surrounded by bullet jacket

Exposed Core base

Visible lead core, surrounded by bullet jacket

What is corning gunpowder?

Wetting it, compressing it, drying it, and grinding it again for more efficient powder

Rebounding Hammer

When the trigger is released after firing, the hammer moves slightly rearward from the fully-forward (fired) position, AUTOMATICALLY introducing a gap between the firing pin and the primer at which point it is blocked from further forward movement without further manipulation of the trigger

Why should you not use a flat bullet for distance shooting?

Wind resistance will cause it to have a tendency deflect off course

Geco

Zinc and titanium based primer (1980's)

Remington Accelerator Cartridge

a cartridge that utilizes a smaller bore diameter projectile held in a bore diameter sleeve

Saboted Bullet

a sub-caliber bullet surrounded by plastic, which is discarded as soon as the projectile leaves the barrel

Neutral Burning Powders

allows burning from inside and outside; burning stays more constant

Higher velocity ammunition contains ___________ to harden the lead

antimony

Physical energy

as hot gases push the projectile, it reacts to the friction and causes torque, recoil, and barrel whip

Chemical Energy

as the propellant converts or decomposes almost completely into a gas.

Hatton rounds are made for ___________

breaching of doorways

Roll Crimp

case neck rolled either into the bullet material or a groove in the bullet to secure it

Remington accelerator cartridges prevent the bullet from touching rifling; what does this do?

causes cartridge to be covered by L&G marks

Where do you mark revolvers?

chamber under the hammer, note where cartridge positioned in the cylinder, note whether the cylinder rotates to the left or right

hammer block safety

common to revolvers with hammer-mounted firing pins from moving through the frame; requires trigger pressure to stay down

Cordite

contains 37% nitrocellulose, 58% nitroglycerine and 5% vaseline

Brenneke slugs

deform less and provide deeper penetration than foster slugs; short range

Transfer Bar

design feature intended to automatically prevent the hammer from contacting the firing pin by introducing a "bar" between them which when impacted by the hammer "transfers" the energy to the firing pin

Hammer Block

differs from the transfer bar in that the falling hammer will impact and come to rest short of the firing position on an otherwise non-functional feature of the assembly unless that feature's blocking action has been removed through the sustained rearward pull of the trigger

Frangible

disintegrate at impact; powdered metal (iron) shaped like the nose

Half Cock

ensures the hammer cannot come in contact with the firing pin

The smaller the grain the _____________ powder burns.

faster

Skid marks

fired from a revolver; short length of rifling on the bullet appearing to be parallel with axis

Wadcutters

flat nosed bullet with a sharp shoulder, to punch out holes in target paper

Hollow Point

generally semi-jacketed; designed to expand on impact with soft targets thus increasing the wounding effect

Degressive Powders

give peak pressures when the bullet is close to the breech and low muzzle pressure; holes

Hook Cutter Rifling

hardened steel cutter is set into a recess in a steel rod of slightly smaller diameter of barrel; as dragged through bore, barrel is rotated; each pass cuts one groove and must be rotated

Flakes (powder)

have a large surface area to burn; preferable for short-barreled, small caliber weapons

Magazine safety

intentional disabling of gun left unattended

Semi-jacketed Bullet

jacket on the side where it comes in contact with the barrel, for high velocity, but still lead at the tip

Stab (ring) crimping

jacketed ammunition; consists of several impressed dimples or a groove pressed into the case mouth by a collet

What does FAAS detect that NAA methods do not?

lead

Lead Lapping

lead plug the same diameter as the bore is repeatedly pulled through rifling whilst being washed with fine abrasive

Identify Hook Cutter Rifling due to?

longitudinal striations in the cut grooves and similarity of micro stria in each of the grooves since same tool is used

Pure Lead bullet noses are only used in ______ _____________ ammunition.

low velocity

Progressive Burning Powders

multi-perforated particles; peak pressure at a point in bullet travel further along muzzle

Transfer bar safety

must be in the up position for energy to be transferred from the hammer to the frame mounted firing pin

More reliable methods for gunshot residue detection include __________________ (NAA), ________________ (FAAS), X ray fluorescence, and photo luminescence techniques.

neutron activation analysis, flameless atomic absorption spectroscopy

Gunshot residue detection methods such as color test for __________ and color tests for _________, ___________, and ___________ have been replaced in recent years.

nitrates; antimony; barium; lead

Sliding Button Safety

operated by a sliding motion ans is typically located on the left side of the firearms frame; when engaged, this safety can block the trigger and can disengage or block the internal gear

Cross Bolt Safety

operated by lateral force on a button, usually located on the trigger guard, prevents the trigger from being pulled

Barium Nitrate primers provides ____________ to increase the temperature of the flame.

oxygen

Wadding

plastic, paper, or fiber material designed to separate the shot from the gunpowder; protect the shot as it is pushed down the barrel

Firing Pin Block

positive blocking of the firing pin preventing its forward movement and which is only removed by sustained trigger pull

Taper Crimp

primarily with cartridge that headspace on the case mouth with lead bullets

Barium, antimony and lead are commonly found in __________ residues.

primer

Pyrodex

propellant introduced in 1970s with similar burning characteristics to black powder but less of the downfalls

Heeled Bullet base

rear of the cartridge case is reduced so that case diameter is the same as the driving surface, usually .22 caliber

Foster slugs may also contain ____________ to allow slug to be swaged down when fired through a choked shotgun barrel

rifling

Grip Safety

secondary safety feature where gun is firmly grasped

Scanning electron microscopy (SEM) makes it possible to establish the __________ and _____________ of the individual gunshot residue particle.

shape; appearance

Foster Slug

short round nosed bullet with a deep cup in the base

Handgun require faster burning powder because of their _____________ ______________.

shorter barrels

The __________ of the case stops travel of the cartridge into the chamber

shoulder

Shotgun slug

single projectile primarily designed to be fired from a smooth-bored shotgun

Trigger safety

small extension on the forward edge of the trigger which must be depressed before the trigger can be pulled

Single-based powder

smokeless propellant by dissolving nitrocellulose with ether and alcohol

For tape collection of gun shot residue SEM tests, important that tape is sticky and ________.

smooth (ensures small particles can easily be observed)

Brenneke Slug

solid lead, pre-rifled projectile with an attached plastic, felt or cellulose fiber wad; provides drag stabilization by moving the centre mass forwards

Buckshot is poor at penetration due to the ____________ __________

spherical shape

A hollow base to a bullet moves center of gravity ___________ the nose, _________________ stability.

towards, increasing

Thumb Safety

usually located on the side of a pistol, it can block the hammer from striking the firing pin, will sometimes de-cock the pistol's hammer, and can disengage the trigger mechanism

Bottle-necked

wide bodied case is reduced in diameter to that of the bullet permitting a larger volume propellant to be used

Tapered case cartridge

wide-based cartridge case is gradually reduced in diameter along its length