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70 Cards in this Set
- Front
- Back
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When is the Breech Ring Condemned?
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After 4500 EFC rds fired.
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When do Cracks condemn the Gun Tube on the interior surface?
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When Cracks exceed 0.125 in (1/8in)
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What is Eccentricity?
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The tendency of the gun tube to widen or "bell mouth" near the muzzle.
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When do Cracks condemn the Gun Tube on the exterior surface?
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When Cracks exceed .25in (1/4in)
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What are the three methods to conduct a recoil exercise?
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M3 Oil Pump
Firing One round (Least Preferred) Gun mount exercise kit |
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Describe the holes in the bore evacuator?
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5 holes equally spaced drilled at a 30 degree angle towards the muzzle.
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What is the Bore Evacuator tested to sustain?
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225 PSI +/- 5 PSI
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When do you notify Direct Support for pitting in the Chamber Region?
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.030 inches deep
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What is the free height of the recoil spring?
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41 inches
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What is the length of the recoil spring during firing?
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12.88 inches
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What is the height of the recoil spring installed?
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24.88 inches
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What are the 3 interior zones the M256A1 divided into?
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Chamber Region
Tapered Zone/Forcing Cone Area Bore |
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What is the spring compression rate for the recoil spring?
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300 LBS/IN
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What should the clearance be between the lug of the operating lever and lug and the top of the operating cam be?
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.005 inches and .010 inches
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When is the ONLY time you set the Operating Cam to the Fast (F) position?
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When the Temperature inside the tank is below 0 degrees Fahrenheit.
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What is the Length of the Tapered Zone?
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18 3/4 inches to 22 inches
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What is the Bore Evacuator called?
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Eccentric Pressure Scavenging System
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What is done when exercising the Hydrospring Recoil System
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It should only be recoiled 6 to 8 inches back and forth three times.
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When should the Hydrospring Recoil System be inspected and exercised?
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At least every 180 days
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What is the Thermal Shroud?
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A form fitting aluminum sleeve that assists in alleviating the effects of thermal bending
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What is the Replenisher?
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Open system, Gravity feed, Self Venting, Translucent plastic replenisher
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How is the Gun Mount Proof fired?
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1 out of 7 gun tubes are tested.
1 Round at low pressure (85%) 0 degrees 1 Round at standard pressure (100%) 70 degrees 1 Round at high pressure (115%) 125 degrees |
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What is Borescope?
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Interior 360 degree visual inspection of the gun tube from the chamber to the muzzle.
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Unpainted External pitting
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.02 inches deep or 80% total surface area
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Painted external pitting
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.04 inches deep or 80% total surface area
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What happens in the Tapered zone/forcing cone zone
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guides the projectile into the bore and compresses the obturator on the projectile resulting in forward obturation
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What is Erosion?
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Is a complex phenomenom resulting from extreme chemical reactions under extreme temperatures and pressure which cause an enlarging or damaging of the bore due to firing.
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What are the 5 phases of function for the M256A1?
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Manual Opening
Automatic Closing Firing Automatic opening Extraction and Ejection |
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What is the length of the M256A1?
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17 ft 4 in
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How much does the bore evacuator weigh?
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28 lbs
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WHat is the weight of the M256A1?
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2502 lbs
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How much does the M256A1 Breech Block weigh?
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225 LBS
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Where is the sling point on the M256A1?
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11 ft 8 in from the muzzle
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What is the M256A1 Bore diameter?
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4.724 in
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How much does the M256A1 Breech ring weigh?
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1506 lbs
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What is Hydrospring?
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The recoil system uses fluid displacement to absorb recoil energy and spring tension to return the gun to battery
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What are the 3 exterior areas the M256A1 divided into?
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Breech Recess Area
External Machined Surfaces Thermal Shroud |
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What is the name of the gun tube?
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M256A1
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What does EFC stand for?
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equivalent full charge
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Where are gun tubes tested?
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Aberdeen Proving Grounds
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What happens at the rear of the chamber region?
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Rear obturation
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What is Cracking?
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Cracks include feathered edges running in an irregular line with varying width and depth.
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What do you use to check if your gun tube may be eccentric?
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Muzzle boresight device
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What does the chrome lining do?
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Extends the life of the gun tube by delaying the erosion of the gun tube base metal.
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The replenisher serves what 3 purposes?
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Allows the crew to monitor the fluid level in the recoil system.
Allows the crew to add or drain fluid as needed. Replenishes the recoil system during firing. |
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What is the Recoil System known as?
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Concentric Hydrospring constant Recoil System.
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Where is the throttling plate located?
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inside the gun cradle near the forward end of the piston
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What is the length of the Chamber Region?
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Begins at the Breech face to a point of 18 3/4 inches into the cannon.
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What is the Gun Cradle?
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Encases the recoil system and does not move with the gun during recoil and counter recoil. It Is sealed at both ends and contains approx. 10.3 Gallons of FRH.
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How many Grooves are in the Throttling Plate?
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8 Grooves machined into it.
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The recoil system serves what 4 purposes?
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To absorb recoil energy.
To provide a fixed length of recoil through all angles of elevation. To return the gun to battery through all angles of elevation. To hold the gun in battery through all angles of elevation. |
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What affects the round inside the bore evacuator
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Round type
Atmospheric Conditions |
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When is the M256A1 condemned?
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1500 EFC rds or 5mm or more wear into the base metal
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What is used to gauge erosion?
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M12 Erosion Gauge
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When should borescoping be done?
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Every 150 EFC round interval after the first 300 RFC rds have been fired.
Within 180 days prior to firing. When Troubleshooting indicates you should. Anytime a cannon tube is installed, even if new. If you are uncertain whether or not a tube has been inspected. |
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How thick is the chrome lining in the gun tube?
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.5 mm thick
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When do you notify Direct support for pitting in the tapered zone?
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.050 inches deep or 20% total surface area.
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What is the Major cause for Gun Tube wear?
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Erosion
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How do you detect erosion?
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By the use of a borescope
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What do you use to borescope?
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M3 Borescope device
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What is the Purpose of of the eccentric pressure scavenging system?
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Removing spent propellant gases from the gun tube.
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describe a piston?
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A machined cylinder that's attached and moves with the gun during recoil and counter recoil
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What is the Recoil System exercise?
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Moving of the piston in the Gun Cradle to reestablish a fluid film between the packing seals and sliding surfaces.
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When does erosion result?
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When the chrome plating on the bore is lost and hot propellant gases wash across the unprotected base metal of the tube bore
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What are the threads on the Breech Recess area called?
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Interrupted butress threads
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What is Concentric?
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The recoil system and the gun tube share a common center.
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What is constant recoil?
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Fixed or constant recoil of 12 inches through all angles of elevation.
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What does the Recoil System consist of?
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Piston
Gun Cradle Recoil Spring Replenisher |
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Describe the Operation of the Chamber and Bore?
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1. Initial detonation, cartridge case combustion
2. Rear obturation 3. Forward obturation by the projectile obturator seal 4. Projectile forward movement 5. Bore Evacuator operation 6. Shot Exit 7. Automatic Breech opening 8. Extraction and Ejection 9. Residual gases evacuated |
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Cam Bracket operating cable adjustment?
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a) Open Breech
b) Safe/Armed handle in the safe position c) Using a feeler gauge, measure the clearance between the Lug of the operating lever and lug and the top of the operating cam. d) The clearance should be between .005 in and .010 in e) If not loose or tighten cable adjustments located at the safe/armed handle or at the back of the breech operating cam arm. f) Recheck the clearance between the operating lever and lug and the operating cam to ensure distance is within tolerance. |
