What is the M240
Air-cooled, gas operated, automatic, firig from an open bolt position
Ammo can capacity
200 rds
Brass catch bag holds?
400 empty cases
Egress kit contents
Shoulder stock, trigger kit, bipod assembly
Caliber
7.62mm
Overall length
41.25in
Weight
26.5lbs
Rate of fire
650-950rds/min
Muzzle velocity
2750 ft/s
Max range
3725m
Max effect range
1200m
Tracer burnout
900m
Employment a/s limit
120kias because of of the abiltiy of the gunner to accurately target the weapon while in the windstream
170kias for the carriage
Purpose of the three settings on gas plug
Maintain consistent rate of fire under adverse conditions, not to increase rate of fire (carbon buildup/cold weather/dusty conditions)
Caution for prolonged firing on setting 2/3
May cause cracks on bolt guide rails
Two types of mounts
-15 & -17
General charactoristics
Air cooled, belt-fed, gas operated, crew served, fully automatic, fires from open bolt.
Max Range
3,725 Meters
Max effective range on area target
1800 Meters
Max effective range on point target
800 Meters
Max effective range for grazing fire
600 Meters
Tracer burn out range
900 Meters
Rounds per burst
6-8 rounds
Rounds per minute
600-650 rounds
Barrel change
After 1 minute
Condition 1
Rounds on feed tray, feed tray cover closed, bolt to the rear, weapon on safe.
Condition 2
Does not apply.
Condition 3
Rounds on feed tray, feed tray cover closed, bolt forward, weapon on fire.
Condition 4
NO rounds on feed tray, feed tray cover closed, bolt forward, weapon on fire.
Major components
Barrel assembly, receiver assembly, butt stock/buffer assembly, bolt/operating rod assembly, trigger housing assembly.
Malfunction
Occurs when a mechanical failure causes the weapon to fire improperly. (Can still fire weapon though)
Stoppage
Any interruption in the cycle of operations caused by faulty action of the weapon or faulty ammunition. (Weapon WILL NOT fire)
Cycle of operations
Feeding, chambering, locking, firing, unlocking, extracting, ejecting, cocking
Muzzle velocity
2750 fps
The GAU?21 is a _______, recoil?operated, automatic weapon firing .50 caliber ammunition from the ______ -bolt position. (300-1)
short/open
Which of the following is not a characteristic of the GAU-21? (300-1)
a. Stellite?coated, chrome?plated barrel
b. Cocking cable at the right side of the machine gun
c. Safety firing assembly on the left side of the machine gun
d. Back plate provided with
b. Cocking cable at the right side of the machine gun
The major assemblies of GAU?21 Machine Gun (Figure 1) are the Barrel Assembly, Receiver Assembly, _______________, Barrel Buffer Assembly, Feed Cover Assembly, __________________, Auxiliary Return Springs Assembly, and Trigger Assembly. (300-1)
bolt assembly/back plate assembly
The GAU-21 has ____ grooves that turn ______.
8/clockwise
What comprises the barrel assembly? (300-3)
barrel and barrel extension
What is the rate of fire for the GAU-21? (300-3)
950 to 1100 rpm
What is the muzzle velocity of the GAU-21? (300-3)
2887 fps
The maximum range is ______ meters and the maximum effective range is_______ meters. (300-3)
6500/1850
The ________________ forms the link between the barrel and the Barrel Buffer Assembly. (300-4)
barrel extension assembly
(T or F): The rear shank of the barrel extension body ensures correct connection with the barrel buffer assembly. (300-4)
TRUE
The barrel extension assembly consists of the Barrel Extension Subassembly and the __________. (300-4)
breech lock
(T or F): To allow rotational movement of the barrel after it has been screwed into position, the forward lug of the locking barrel spring blade engages one of the locking grooves located in the rear of the barrel. (300-4)
FALSE
The _________Assembly and ___________Assembly support, protect, and house various assemblies of the GAU-21 Machine Gun. (300-6)
receiver/barrel jacket
(T or F): The Belt Holding Pawls Assembly (Figure 3) and the Feed Tray contribute to the correct feeding of the ammunition belt. (300-6)
TRUE
The ______________, fitted into its housing in the bottom of the Receiver Subassembly is used to guide the Breech Lock. (300-6)
breech lock cam
The ___________________, which is secured to the lower left rear side of the receiver subassembly, is used to pull the bolt assembly to the rear of the receiver assembly into the cocked position. (300-8)
manual cocking assembly
The ___________Assembly is used to hold back the Bolt Assembly, at the rear of the receiver assembly, in the open/cocked position. (300-10)
bolt latch
When the __________ is depressed, the bolt latch is raised by the Bolt Latch Pawl so that it releases the bolt assembly if the bolt is at its rear position. (300-10)
firing lever
When the Safety Firing Assembly is at the upper FIRE position, the ________ is blocked in the outward position by the GAU-21 Timing Adjusting Screw. (300-10)
firing cam
(T or F): When, at the end of the forward movement of the bolt assembly, the Sear Slide comes into contact with the blocked cam, the slide will be forced to move right into the Sear, releasing the Extension Firing Pin Assembly. (300-10)
TRUE
(T or F):The Extractor Assembly controls the feeding, extracting, and ejecting operation, as well as operation of the Firing Pin. (300-12)
FALSE
The __________ is used to push the Extension Firing Pin Assembly into its cocked position. (300-12)
cocking lever
The extension firing pin assembly, when released by the _______, impacts the ammunition primer, firing the round. (300-12)
sear
The _________________ Assembly is used to hold back the rear of the Firing Pin Spring when the extension firing pin assembly is in the cocked position. This allows the firing pin spring to be compressed within the Firing Pin Extension. (300-12)
firing pin extension spring stop
The ________ is used to hold the extension firing pin assembly back at its cocked position and is released by the Sear Slide during the firing sequence. (300-12)
sear
(T or F): The ejector subassemblies remove a round of ammunition from a linked belt while guiding the round into the T-slot of the bolt assembly. The extractor pushes the expended round from the T-slot and ejects the round from the bottom of the receiver
FALSE
The ___________ Assembly (Figure 7) absorbs the recoil energy of the barrel assembly. (300-14)
barrel buffer
The __________ and the Buffer Block Subassembly ensure correct locking with the barrel extension assembly. (300-14)
buffer accelerator
(T or F): The vertical position of the handle of the cover latch shaft assembly ensures the feed cover assembly cannot be opened when the safety firing assembly is at the (upper) FIRE position. (300-16)
TRUE
The ______________ is guided by the fore and aft movement of the bolt assembly, which allows the feed slide and pawl assembly to move from side to side and push ammunition into the weapon. (300-16)
belt feed lever
The _______________, mounted onto the rear section of the receiver assembly, is used to stop the bolt assembly at the end of its rearward movement and to absorb its remaining recoil energy. (300-18)
back plate assembly
(T or F): The Back Plate Latch Lock, held in a spring-tension position by the Back Plate Latch Lock Spring, is used to lock the Back Plate Latch so that it becomes impossible to accidentally release the back plate assembly by inadvertently moving the back
TRUE
The ________________ assists the rod assembly when pushing the bolt assembly toward the front position, to ensure there is enough force to pull the ammunition belt correctly into the machine gun. (300-20)
auxiliary return spring assembly
Which of the following is not one of the actions in the counter recoil phase? (400-1)
cocking
The recoil phase consists of: (400-1
unlocking, extracting, ejecting, cocking
The cycle of operation begins with the ______________. (400-1)
counter recoil phase
(T or F): Firing is a continuous process that occurs throughout the cycle of operation. (400-2)
FALSE
As the bolt moves forward, the extractor rides underneath the _________, ensuring the cartridge is positioned in front of the recessed firing pin and inserted into the chamber of the barrel. (400-2)
extractor switch
The insertion depth of the chambered cartridge is controlled by the __________. (400-2)
headspace adjustment
(T or F): Locking of the breech occurs when the bolt locks to the barrel extension. (400-3)
TRUE
(T or F): The counter-recoil phase is initiated by the rapidly expanding gases generated as a bullet is being fired. (400-3)
FALSE
Cocking occurs when the cocking lever on the bolt contacts the ____________on the receiver. (400-4)
bolt latch bracket
(T or F): The adjusted tension of the spring washers will dictate how fast or slowly the regulator tube stops the rearward movement of the bolt, and it will have a direct effect on the rate of fire for the weapon. (400-4)
TRUE
A ___________ is defined as "any interruption in the cycle of operation caused by the faulty action of the weapon or ammunition" and a _____________ is defined as "a part bending, breaking, or being worn to the point of being non? operational." (400-4)
stoppage/malfunction
When the Breech Bolt is unlocked, the barrel assembly ________________________.
(400-5)
is no longer connected to the bolt
(T or F): When the Breech Lock is fully engaged in the recess in the bottom of the breech bolt, approximately 0.590 inch (14.9 mm) before the end of the forward movement of the bolt assembly, the breech bolt is said to be "locked" to the Barrel Extension
TRUE
(T or F): When the bolt assembly reaches its most forward position, the next cartridge will be fired if the safety firing assembly is at the (lower) FIRE position. (400-8)
FALSE
Where is the extractor spring mounted? (400-10)
inside the feed cover assembly
When the firing safety selector is placed in the safe (lower) position, the GAU-21 timing screw is________________________________. (400-13)
is not at the same level of the rear end of the firing cam.
When the firing safety selector is placed in the fire (upper) position, the GAU-21 timing screw is at the same level of the rear end of the firing cam so that firing cam is____________ by the screw. (400-14)
blocked
After cocking the machine gun or after interrupting the shoring, the breech bolt is held back at its rear position by the______________. (400-15)
bolt latch
(T or F): (Disassembly) Ensure the bolt assembly is at the forward position to release pressure on the rod spring assembly so the spring can be removed safely. Failure to do so could result in injury to personnel. (500-4)
TRUE
(Reassembly) When reinstalling the bolt assembly and extractor assembly into the receiver, it is absolutely necessary that the cocking lever is at its _________ position. (500-21)
forward
(T or F): Firing rate decreases when parts of the machine gun are broken in and the weapon is hot. (600-4)
FALSE
Headspace is the distance between the ________of the T?slot for the cartridges on the front face of the_________ and a particular point on the front part of the cartridge case. (600-5)
bottom/bolt
A too?large headspace can result in all of the following except: (600-5)
Can result in a failure to lock the bolt
To adjust headspace, when viewed from rear of weapon, turn Barrel ________________to tighten. (600-8)
counterclockwise
Timing adjustment ensures _______________. (600-9)
the cartridge is not fired too early or too late.
(T or F): Too?early firing could cause serious damage to the front part of the Receiver, Barrel Extension Assembly, and front face of the bolt. (600-9)
FALSE
(Troubleshooting). If the GAU-21 fails to lock, which of the following is a probable cause? (600-14)
headspace too small
(Troubleshooting). If the GAU-21 fails to fire, which of the following is not a probable cause? (600-15)
Headspace too large.
(Troubleshooting). If the GAU-21 has sheared casings, which of the following is a possible solution? (600-15)
Replace extractor and Check and gauge headspace
(Troubleshooting). If the GAU-21 stops firing in battery (full forward) position with no cartridge in chamber all of the following are probable causes except: (600-16)
Headspace too small
Avoid clearing the gun in the _________ position and always ensure the weapon is pointed in a safe direction. (GAU-21 CL-2)
stowed
(T or F): Failure to notify weapons personnel of missing, loose, or damaged components may result in a catastrophic weapon malfunction. (GAU-21 CL-2)
TRUE
Allow the gun to cool prior to stowing to avoid the possibility of a __________. (GAU-21 CL-2)
cook off
(T or F): The GAU-21 may armed and loaded in the stowed position only if preparing to do an AIE. (GAU-21 CL-2)
false
Minimum ____minutes of cooling is required after firing a total ______rounds.
(GAU-21 CL-2)
2/300
Allow _____minutes of cooling after firing ______total rounds to provide complete cooling of the barrel. Complete cooling is mandatory to ensure maximum safety and barrel life. (GAU-21 CL-2)
10/600
When should the fire safety selector switch be placed to "Fire" when arming the GAU-21? (GAU-21 CL-2)
after you report "tail gun armed and ready to fire.
(T or F): After AIEs operations are complete, re-accomplish ARMING PROCEDURES checklist in order to continue firing. (GAU-21 CL-2)
TRUE
What is required during NVG operations to verify the GAU-21 is clear of ammunition? (GAU-21 CL-2)
adequate light and eye protection
A ____________ is when the trigger(s) are depressed/squeezed and the gun does not do fire, or fires rounds and then stops firing, or jams for an unknown reason. (GAU-21 CL-2)
stoppage
A _____________ occurs when the primer of the ammunition round has detonated after being struck by the firing pin, but some problem with the propellant powder causes it to burn too slowly. (GAU-21 CL-2)
hangfire
A ___________ is the complete failure of the weapon to fire. (GAU-21 CL-2)
misfire
A _____________ occurs when the heat of the barrel is high enough to cause the propellant powder inside the round to ignite, even though the primer has not been struck by the firing pin. (GAU-21 CL-2)
cookoff
Common causes of a runaway gun are a malfunctioning _____________________. (GAU-21 CL-2)
sear or trigger mechanism
(T or F): When clearing weapon stoppages, you must open the feed cover of a weapon that is considered to be in a "hot gun" condition, or death/injury to personnel may result. (GAU-21 CL-2)
FALSE
When more than ____ rounds have been fired in a ___-minute period, the barrel is hot enough to produce a cook-off. If there is a round chambered, the weapon is considered to be in a "hot gun" condition, and no further steps will be accomplished until ____
150/two/five
(T or F): Do not attempt to grab or place anything into the ammo belt when attempting to stop a runaway gun. (GAU-21 CL-2)
TRUE
(T or F): In a runaway gun condition, placing the GAU-21 on SAFE will prevent the bolt from going into battery. If a live round is present, and the gun is hot, there is no potential for cook-off. (GAU-21 CL-2)
FALSE
Fire only at targets not identified as FRIENDLY IAW current ROE is which weapons control status? (3-3 pg. 8-1)
weapons free
Fire only at targets positively identified as HOSTILE IAW current ROE. (3-3 pg. 8-1)
weapons tight
Fire only in self-defense or in response to a formal order. (3-3 pg. 8-1)
weapons hold/safe
The GAU-21 has ___ degrees azimuth left and right. (3-3 pg. 8-2)
66
The GAU-21 has ___ degrees elevation. (3-3 pg. 8-2)
60
What is the firing fan limitation on the ground? Direction is based on aircraft's left and right (3-3 pg. 8-2)
6 degrees right, 126 degrees left
______________ are the factors within the barrel affecting the motion of the projectile before it leaves the barrel. (3-3 pg. 8-3)
Interior ballistics
Which of the following is not a factor of interior ballistics? (3-3 pg. 8-3)
air resistance (drag)
________________ are the factors that affect projectile motion along the trajectory. (3-3 pg. 8-3)
Exterior ballistics
Which of the following is a factor of exterior ballistics? (3-3 pg. 8-3)
a. air resistance (drag)
b. yaw/gravity
c. wind/projectile drift
US projectiles, as viewed from the rear, spin in a ___________ direction. A spinning projectile acts as a gyroscope and exhibits the characteristic known as __________________. (3-3 pg. 8-4)
clockwise/gyroscopic precession
____________ pertain to the characteristics and effects of projectiles at the point of impact. (3-3 pg. 8-7)
Terminal ballistics
The GAU-21 tracer round burns out at approximately _______ meters. (3-3 pg. 8-8)
1500
(T or F): Consistently flying in trail allows the enemy to place raking fire across the formation, and observation of the team is reduced. (3-3 pg. 8-9)
TRUE
A good rule of thumb for assigning a percentage for the ammo on a mission is to have 25 percent for ingress, 50 percent for the terminal area, and the other 25 percent for egress. (3-3 pg. 8-9)
25/50/25
Minimum Engagement Distances may be specified by a range instruction. In the absence of such guidance, the recommended minimum engagement distances for the GAU-21 is________ feet. (3-3 pg. 8-10)
1000
The maximum range of a .50 caliber round is over ______ miles. (3-3 pg. 8-10)
4
(No-Fire Areas) Avoid the following while firing: (3-3 pg. 8-13)
a. Firing across the nose (or flightpath) of another aircraft in the formation.
b. Firing at a target silhouetted by a friendly aircraft.
c. Firing at targets within the minimum engagement range of the weapon.
Tail Scanners must keep the aircraft commander apprised of the which of the following: (3-3 pg. 8-16)
a. Position of wingmen/team.
b. Weapons and Ammunition status.
c. Threats
Auxiliary Return Spring
Back Plate and Buffer Assembly
Barrel and Barrel Extension Assembly
Barrel Jacket Assembly
Breech Bolt and Rod Assembly
Dust Cover
Feed Cover Assembly
Receiver Assembly
Recoil Buffer Assembly
Trigger Assembly
Rate of Fire
1025 +/- 75 RPM
Muzzle Velocity
2887 fps
Effective Range
1850 meters
Maximum Range
6500 meters
Weight
80 lbs
Barrel Twist
Right-hand 15.0
M240 Armor Piercing Color (M993)
Black Tip
M240 Tracer (M17)
Orange Tip
M240 Dim Tracer (M276)
Green tip/white ring
Gau-21Tracer(M17)
orange
Gau-21 Dim Tracer (M257)
Lavender
Gau-21 Armor Piercing Incendiary (M20)
red/orange tip, silver ring
Gau-21 Armor Piercing Explosive Incendiary (Mk211)
green tip
What is the M240
Air-cooled, gas operated, automatic, firig from an open bolt position
Ammo can capacity
200 rds
Brass catch bag holds?
400 empty cases
Egress kit contents
Shoulder stock, trigger kit, bipod assembly
Caliber
7.62mm
Overall length
41.25in
Weight
26.5lbs
Rate of fire
650-950rds/min
Muzzle velocity
2750 ft/s
Max range
3725m
Max effect range
1200m
Tracer burnout
900m
Employment a/s limit
120kias because of of the abiltiy of the gunner to accurately target the weapon while in the windstream
170kias for the carriage
Purpose of the three settings on gas plug
Maintain consistent rate of fire under adverse conditions, not to increase rate of fire (carbon buildup/cold weather/dusty conditions)
Caution for prolonged firing on setting 2/3
May cause cracks on bolt guide rails
Two types of mounts
-15 & -17
General charactoristics
Air cooled, belt-fed, gas operated, crew served, fully automatic, fires from open bolt.
Max Range
3,725 Meters
Max effective range on area target
1800 Meters
Max effective range on point target
800 Meters
Max effective range for grazing fire
600 Meters
Tracer burn out range
900 Meters
Rounds per burst
6-8 rounds
Rounds per minute
600-650 rounds
Barrel change
After 1 minute
Condition 1
Rounds on feed tray, feed tray cover closed, bolt to the rear, weapon on safe.
Condition 2
Does not apply.
Condition 3
Rounds on feed tray, feed tray cover closed, bolt forward, weapon on fire.
Condition 4
NO rounds on feed tray, feed tray cover closed, bolt forward, weapon on fire.
Major components
Barrel assembly, receiver assembly, butt stock/buffer assembly, bolt/operating rod assembly, trigger housing assembly.
Malfunction
Occurs when a mechanical failure causes the weapon to fire improperly. (Can still fire weapon though)
Stoppage
Any interruption in the cycle of operations caused by faulty action of the weapon or faulty ammunition. (Weapon WILL NOT fire)
Cycle of operations
Feeding, chambering, locking, firing, unlocking, extracting, ejecting, cocking
Muzzle velocity
2750 fps
The GAU?21 is a _______, recoil?operated, automatic weapon firing .50 caliber ammunition from the ______ -bolt position. (300-1)
short/open
Which of the following is not a characteristic of the GAU-21? (300-1)
a. Stellite?coated, chrome?plated barrel
b. Cocking cable at the right side of the machine gun
c. Safety firing assembly on the left side of the machine gun
d. Back plate provided with
b. Cocking cable at the right side of the machine gun
The major assemblies of GAU?21 Machine Gun (Figure 1) are the Barrel Assembly, Receiver Assembly, _______________, Barrel Buffer Assembly, Feed Cover Assembly, __________________, Auxiliary Return Springs Assembly, and Trigger Assembly. (300-1)
bolt assembly/back plate assembly
The GAU-21 has ____ grooves that turn ______.
8/clockwise
What comprises the barrel assembly? (300-3)
barrel and barrel extension
What is the rate of fire for the GAU-21? (300-3)
950 to 1100 rpm
What is the muzzle velocity of the GAU-21? (300-3)
2887 fps
The maximum range is ______ meters and the maximum effective range is_______ meters. (300-3)
6500/1850
The ________________ forms the link between the barrel and the Barrel Buffer Assembly. (300-4)
barrel extension assembly
(T or F): The rear shank of the barrel extension body ensures correct connection with the barrel buffer assembly. (300-4)
TRUE
The barrel extension assembly consists of the Barrel Extension Subassembly and the __________. (300-4)
breech lock
(T or F): To allow rotational movement of the barrel after it has been screwed into position, the forward lug of the locking barrel spring blade engages one of the locking grooves located in the rear of the barrel. (300-4)
FALSE
The _________Assembly and ___________Assembly support, protect, and house various assemblies of the GAU-21 Machine Gun. (300-6)
receiver/barrel jacket
(T or F): The Belt Holding Pawls Assembly (Figure 3) and the Feed Tray contribute to the correct feeding of the ammunition belt. (300-6)
TRUE
The ______________, fitted into its housing in the bottom of the Receiver Subassembly is used to guide the Breech Lock. (300-6)
breech lock cam
The ___________________, which is secured to the lower left rear side of the receiver subassembly, is used to pull the bolt assembly to the rear of the receiver assembly into the cocked position. (300-8)
manual cocking assembly
The ___________Assembly is used to hold back the Bolt Assembly, at the rear of the receiver assembly, in the open/cocked position. (300-10)
bolt latch
When the __________ is depressed, the bolt latch is raised by the Bolt Latch Pawl so that it releases the bolt assembly if the bolt is at its rear position. (300-10)
firing lever
When the Safety Firing Assembly is at the upper FIRE position, the ________ is blocked in the outward position by the GAU-21 Timing Adjusting Screw. (300-10)
firing cam
(T or F): When, at the end of the forward movement of the bolt assembly, the Sear Slide comes into contact with the blocked cam, the slide will be forced to move right into the Sear, releasing the Extension Firing Pin Assembly. (300-10)
TRUE
(T or F):The Extractor Assembly controls the feeding, extracting, and ejecting operation, as well as operation of the Firing Pin. (300-12)
FALSE
The __________ is used to push the Extension Firing Pin Assembly into its cocked position. (300-12)
cocking lever
The extension firing pin assembly, when released by the _______, impacts the ammunition primer, firing the round. (300-12)
sear
The _________________ Assembly is used to hold back the rear of the Firing Pin Spring when the extension firing pin assembly is in the cocked position. This allows the firing pin spring to be compressed within the Firing Pin Extension. (300-12)
firing pin extension spring stop
The ________ is used to hold the extension firing pin assembly back at its cocked position and is released by the Sear Slide during the firing sequence. (300-12)
sear
(T or F): The ejector subassemblies remove a round of ammunition from a linked belt while guiding the round into the T-slot of the bolt assembly. The extractor pushes the expended round from the T-slot and ejects the round from the bottom of the receiver
FALSE
The ___________ Assembly (Figure 7) absorbs the recoil energy of the barrel assembly. (300-14)
barrel buffer
The __________ and the Buffer Block Subassembly ensure correct locking with the barrel extension assembly. (300-14)
buffer accelerator
(T or F): The vertical position of the handle of the cover latch shaft assembly ensures the feed cover assembly cannot be opened when the safety firing assembly is at the (upper) FIRE position. (300-16)
TRUE
The ______________ is guided by the fore and aft movement of the bolt assembly, which allows the feed slide and pawl assembly to move from side to side and push ammunition into the weapon. (300-16)
belt feed lever
The _______________, mounted onto the rear section of the receiver assembly, is used to stop the bolt assembly at the end of its rearward movement and to absorb its remaining recoil energy. (300-18)
back plate assembly
(T or F): The Back Plate Latch Lock, held in a spring-tension position by the Back Plate Latch Lock Spring, is used to lock the Back Plate Latch so that it becomes impossible to accidentally release the back plate assembly by inadvertently moving the back
TRUE
The ________________ assists the rod assembly when pushing the bolt assembly toward the front position, to ensure there is enough force to pull the ammunition belt correctly into the machine gun. (300-20)
auxiliary return spring assembly
Which of the following is not one of the actions in the counter recoil phase? (400-1)
cocking
The recoil phase consists of: (400-1
unlocking, extracting, ejecting, cocking
The cycle of operation begins with the ______________. (400-1)
counter recoil phase
(T or F): Firing is a continuous process that occurs throughout the cycle of operation. (400-2)
FALSE
As the bolt moves forward, the extractor rides underneath the _________, ensuring the cartridge is positioned in front of the recessed firing pin and inserted into the chamber of the barrel. (400-2)
extractor switch
The insertion depth of the chambered cartridge is controlled by the __________. (400-2)
headspace adjustment
(T or F): Locking of the breech occurs when the bolt locks to the barrel extension. (400-3)
TRUE
(T or F): The counter-recoil phase is initiated by the rapidly expanding gases generated as a bullet is being fired. (400-3)
FALSE
Cocking occurs when the cocking lever on the bolt contacts the ____________on the receiver. (400-4)
bolt latch bracket
(T or F): The adjusted tension of the spring washers will dictate how fast or slowly the regulator tube stops the rearward movement of the bolt, and it will have a direct effect on the rate of fire for the weapon. (400-4)
TRUE
A ___________ is defined as "any interruption in the cycle of operation caused by the faulty action of the weapon or ammunition" and a _____________ is defined as "a part bending, breaking, or being worn to the point of being non? operational." (400-4)
stoppage/malfunction
When the Breech Bolt is unlocked, the barrel assembly ________________________.
(400-5)
is no longer connected to the bolt
(T or F): When the Breech Lock is fully engaged in the recess in the bottom of the breech bolt, approximately 0.590 inch (14.9 mm) before the end of the forward movement of the bolt assembly, the breech bolt is said to be "locked" to the Barrel Extension
TRUE
(T or F): When the bolt assembly reaches its most forward position, the next cartridge will be fired if the safety firing assembly is at the (lower) FIRE position. (400-8)
FALSE
Where is the extractor spring mounted? (400-10)
inside the feed cover assembly
When the firing safety selector is placed in the safe (lower) position, the GAU-21 timing screw is________________________________. (400-13)
is not at the same level of the rear end of the firing cam.
When the firing safety selector is placed in the fire (upper) position, the GAU-21 timing screw is at the same level of the rear end of the firing cam so that firing cam is____________ by the screw. (400-14)
blocked
After cocking the machine gun or after interrupting the shoring, the breech bolt is held back at its rear position by the______________. (400-15)
bolt latch
(T or F): (Disassembly) Ensure the bolt assembly is at the forward position to release pressure on the rod spring assembly so the spring can be removed safely. Failure to do so could result in injury to personnel. (500-4)
TRUE
(Reassembly) When reinstalling the bolt assembly and extractor assembly into the receiver, it is absolutely necessary that the cocking lever is at its _________ position. (500-21)
forward
(T or F): Firing rate decreases when parts of the machine gun are broken in and the weapon is hot. (600-4)
FALSE
Headspace is the distance between the ________of the T?slot for the cartridges on the front face of the_________ and a particular point on the front part of the cartridge case. (600-5)
bottom/bolt
A too?large headspace can result in all of the following except: (600-5)
Can result in a failure to lock the bolt
To adjust headspace, when viewed from rear of weapon, turn Barrel ________________to tighten. (600-8)
counterclockwise
Timing adjustment ensures _______________. (600-9)
the cartridge is not fired too early or too late.
(T or F): Too?early firing could cause serious damage to the front part of the Receiver, Barrel Extension Assembly, and front face of the bolt. (600-9)
FALSE
(Troubleshooting). If the GAU-21 fails to lock, which of the following is a probable cause? (600-14)
headspace too small
(Troubleshooting). If the GAU-21 fails to fire, which of the following is not a probable cause? (600-15)
Headspace too large.
(Troubleshooting). If the GAU-21 has sheared casings, which of the following is a possible solution? (600-15)
Replace extractor and Check and gauge headspace
(Troubleshooting). If the GAU-21 stops firing in battery (full forward) position with no cartridge in chamber all of the following are probable causes except: (600-16)
Headspace too small
Avoid clearing the gun in the _________ position and always ensure the weapon is pointed in a safe direction. (GAU-21 CL-2)
stowed
(T or F): Failure to notify weapons personnel of missing, loose, or damaged components may result in a catastrophic weapon malfunction. (GAU-21 CL-2)
TRUE
Allow the gun to cool prior to stowing to avoid the possibility of a __________. (GAU-21 CL-2)
cook off
(T or F): The GAU-21 may armed and loaded in the stowed position only if preparing to do an AIE. (GAU-21 CL-2)
false
Minimum ____minutes of cooling is required after firing a total ______rounds.
(GAU-21 CL-2)
2/300
Allow _____minutes of cooling after firing ______total rounds to provide complete cooling of the barrel. Complete cooling is mandatory to ensure maximum safety and barrel life. (GAU-21 CL-2)
10/600
When should the fire safety selector switch be placed to "Fire" when arming the GAU-21? (GAU-21 CL-2)
after you report "tail gun armed and ready to fire.
(T or F): After AIEs operations are complete, re-accomplish ARMING PROCEDURES checklist in order to continue firing. (GAU-21 CL-2)
TRUE
What is required during NVG operations to verify the GAU-21 is clear of ammunition? (GAU-21 CL-2)
adequate light and eye protection
A ____________ is when the trigger(s) are depressed/squeezed and the gun does not do fire, or fires rounds and then stops firing, or jams for an unknown reason. (GAU-21 CL-2)
stoppage
A _____________ occurs when the primer of the ammunition round has detonated after being struck by the firing pin, but some problem with the propellant powder causes it to burn too slowly. (GAU-21 CL-2)
hangfire
A ___________ is the complete failure of the weapon to fire. (GAU-21 CL-2)
misfire
A _____________ occurs when the heat of the barrel is high enough to cause the propellant powder inside the round to ignite, even though the primer has not been struck by the firing pin. (GAU-21 CL-2)
cookoff
Common causes of a runaway gun are a malfunctioning _____________________. (GAU-21 CL-2)
sear or trigger mechanism
(T or F): When clearing weapon stoppages, you must open the feed cover of a weapon that is considered to be in a "hot gun" condition, or death/injury to personnel may result. (GAU-21 CL-2)
FALSE
When more than ____ rounds have been fired in a ___-minute period, the barrel is hot enough to produce a cook-off. If there is a round chambered, the weapon is considered to be in a "hot gun" condition, and no further steps will be accomplished until ____
150/two/five
(T or F): Do not attempt to grab or place anything into the ammo belt when attempting to stop a runaway gun. (GAU-21 CL-2)
TRUE
(T or F): In a runaway gun condition, placing the GAU-21 on SAFE will prevent the bolt from going into battery. If a live round is present, and the gun is hot, there is no potential for cook-off. (GAU-21 CL-2)
FALSE
Fire only at targets not identified as FRIENDLY IAW current ROE is which weapons control status? (3-3 pg. 8-1)
weapons free
Fire only at targets positively identified as HOSTILE IAW current ROE. (3-3 pg. 8-1)
weapons tight
Fire only in self-defense or in response to a formal order. (3-3 pg. 8-1)
weapons hold/safe
The GAU-21 has ___ degrees azimuth left and right. (3-3 pg. 8-2)
66
The GAU-21 has ___ degrees elevation. (3-3 pg. 8-2)
60
What is the firing fan limitation on the ground? Direction is based on aircraft's left and right (3-3 pg. 8-2)
6 degrees right, 126 degrees left
______________ are the factors within the barrel affecting the motion of the projectile before it leaves the barrel. (3-3 pg. 8-3)
Interior ballistics
Which of the following is not a factor of interior ballistics? (3-3 pg. 8-3)
air resistance (drag)
________________ are the factors that affect projectile motion along the trajectory. (3-3 pg. 8-3)
Exterior ballistics
Which of the following is a factor of exterior ballistics? (3-3 pg. 8-3)
a. air resistance (drag)
b. yaw/gravity
c. wind/projectile drift
US projectiles, as viewed from the rear, spin in a ___________ direction. A spinning projectile acts as a gyroscope and exhibits the characteristic known as __________________. (3-3 pg. 8-4)
clockwise/gyroscopic precession
____________ pertain to the characteristics and effects of projectiles at the point of impact. (3-3 pg. 8-7)
Terminal ballistics
The GAU-21 tracer round burns out at approximately _______ meters. (3-3 pg. 8-8)
1500
(T or F): Consistently flying in trail allows the enemy to place raking fire across the formation, and observation of the team is reduced. (3-3 pg. 8-9)
TRUE
A good rule of thumb for assigning a percentage for the ammo on a mission is to have 25 percent for ingress, 50 percent for the terminal area, and the other 25 percent for egress. (3-3 pg. 8-9)
25/50/25
Minimum Engagement Distances may be specified by a range instruction. In the absence of such guidance, the recommended minimum engagement distances for the GAU-21 is________ feet. (3-3 pg. 8-10)
1000
The maximum range of a .50 caliber round is over ______ miles. (3-3 pg. 8-10)
4
(No-Fire Areas) Avoid the following while firing: (3-3 pg. 8-13)
a. Firing across the nose (or flightpath) of another aircraft in the formation.
b. Firing at a target silhouetted by a friendly aircraft.
c. Firing at targets within the minimum engagement range of the weapon.
Tail Scanners must keep the aircraft commander apprised of the which of the following: (3-3 pg. 8-16)
a. Position of wingmen/team.
b. Weapons and Ammunition status.
c. Threats
Auxiliary Return Spring
Back Plate and Buffer Assembly
Barrel and Barrel Extension Assembly
Barrel Jacket Assembly
Breech Bolt and Rod Assembly
Dust Cover
Feed Cover Assembly
Receiver Assembly
Recoil Buffer Assembly
Trigger Assembly
Rate of Fire
1025 +/- 75 RPM
Muzzle Velocity
2887 fps
Effective Range
1850 meters
Maximum Range
6500 meters
Weight
80 lbs
Barrel Twist
Right-hand 15.0
M240 Armor Piercing Color (M993)
Black Tip
M240 Tracer (M17)
Orange Tip
M240 Dim Tracer (M276)
Green tip/white ring
Gau-21Tracer(M17)
orange
Gau-21 Dim Tracer (M257)
Lavender
Gau-21 Armor Piercing Incendiary (M20)
red/orange tip, silver ring
Gau-21 Armor Piercing Explosive Incendiary (Mk211)
green tip