Terms Flashcards
Breech
The outside, rear face of the barrel which meets the face of the bolt or breechblock
Breechblock
The component that seals the breech and blocks gases from the fired cartridge from exiting to the rear of the chamber.
Bolts in rifles and MG’s.
Inside of the slide in pistols.
Cartridge
Consists of the cartridge case and the bullet.
Headspace
The distance from the breechblock to the part of the chamber that stops the forward movement of the cartridge case.
All Weapons have headspace.
Three Ways to Measure Headspace
Slide Face- Pistol
Rimmed Case- PKM
Rimless Case- M4
Types of Headspace Gauges
Go Gauge
No Go Gauge
Field Gauge
Go Gauge
This gauge will fit the weapon’s headspace and the weapon will chamber as normal.
No Go Gauge
This gauge should not fit the weapon’s headspace; therefore the weapon should not camber properly or lock.
If this gauge does fit the weapon’s headspace then the weapon is no longer serviceable because the headspace has expanded most likely due to extreme usage.
Field Gauge
This is used to determine when a weapon is outside of its specs and no longer used.
Muzzle Break
A device at the end of the weapon which deflects the gases as they exit the muzzle of the weapon; this in turn helps to reduce some of the rearward felt recoil.
4 Types of Muzzle Devices
Flash Hider
Muzzle Brake
Compensator
Hybrid
Flash Hider
Found on short barreled rifles.
Used because the propellant is still burning as the bullet leaves the barrel (which creates a fireball effect).
Muzzle Brake
Deflects powder gases as they exit the weapon. Also helps reduce recoil.
Compensator
Aid in reducing recoil, rise, and recoil felt by the shooter.
Hybrid
Combines characteristics from any other two categories of Muzzle Devices.
Fluted Chamber
Slots cut in the chamber of a weapon which allow for gases from the fired cartridge to enter the chamber. These gases create a buffer between the cartridge case and the chamber wall that aids in the extraction of the cartridge case from the chamber.
A fluted chamber will leave horizontal “burn” marks on the spent cartridge case produced by the gases that cycle the weapon.
The purpose of a Fluted Chamber is to ensure the extraction of the cartridge case.
Rifling
Helix grooves in the bore of the weapon which spin the bullet for accuracy.
Lands
The raised portion between the grooves in the bore of a gun that impart the spinning motion to a bullet.
Grooves
The valley portion of the rifling in a barrel that in conjunction with the lands impart the spinning motion to a bullet.
Twist Ratio
1 Turn: # of inches required
1:7= 1 turn for every seven inches traveled by the bullet.
Larger ratios are required to accurately shoot lighter rounds.
A round will be unstable in flight if you do not use the properly weighted rounds with the corresponding twist ratio.
How Rifling Is Made
- Cutting one groove at a time with a machine tool. (Cut Rifling or Single Point Cut Rifling)
- Cutting all of the grooves in one pass with a special progressive breeching bit. (Broached Rifling)
- Pressing all of the grooves at once with a tool called a “button” that is pushed or pulled down the barrel. (Button Rifling)
- Forging the Barrel
- Flow forming the Barrel
Polygonal Rifling
*Lasts 5-10% longer than traditional rifling.
*Optimum caliber- .45 ACP
2 Types- Hexagonal, Octagonal
Extractor
A component which attaches to the rear of the cartridge groove or rim which is used to pull the cartridge from the chamber.
Ejector
A cam or projection inside the receiver against which the cartridge case strikes and is thrown clear of the mechanism after it has been drawn from the chamber by the extractor.
- Found 180 degrees/ opposite from the ejection port
- May also be a tang of metal attached to the Receiver, (common on pistols) this is normally indicated by the cut out on the bolt group
- AK has a groove on the bolt that acts as its ejector
Disconnector
A device which prevents the firing of more than one round for one pull of the trigger or prevents the weapon from being fired until the action is fully closed/ the weapon is in full battery.
Sear
Component retained under spring tension that releases, by means of a trigger, either a firing pin, hammer, or bolt.
Battle Sight
The range at which you can hit a target between the throat and waist without making a sight adjustment.
Choke
An inside bore constriction at the muzzle end of the shotgun’s barrel.
*When a shot shell is fired, the shot travels down the bore, exits the muzzle, and begins to spread out. Chokes also increase effective range of the weapon.
Trigger Bar
A connecting bar operating between the trigger and the sear. Nothing more than an extension of the trigger.
Trigger
A finger actuated level used to activate the firing mechanism firing the weapon.
Chamber
The unrifled portion of the bore at the rear end of the barrel that receives and supports the cartridge when the breach is closed. The chamber aligns the bullet with the bore and the primer with the firing pin.
Firing Pin
The part of the firing mechanism that strikes or contacts the primer of the cartridge to cause ignition to fire the weapon.
Compensator
A component at the muzzle end of a weapon that has slots in the top to vent gases from a fired cartridge upward as they live the barrel. The bottom of the component is solid in order to use the gases from the fired cartridge to force the barrel of the weapon downward.
