Gun Tube Tech Flashcards
Zone 3
Bore. The bore is the rest of the interior of the cannon starting at 22 inches from the breech face.
Breach Recess Area
Threaded end of the cannon that is inserted into the breech ring. This area contains the interrupted buttress threads.
Zone 2
Tapered zone. Zone 2 is the area starting at 18-3/4 inches and ending at 22 inches into the cannon. Zone 2 is 3-1/4 inches long. The tapered zone is the transition between the chamber and the bore which guides the projectile into the bore and compresses the obturator on the projectile resulting in forward obturation.
Zone 1
Chamber region, the chamber region begins at the breech face of the tube to a point of 18-3/4 inches into the cannon. At the rear of the chamber region, rear obturation occurs
Recoil Spring Specs
Free height - 41 inches
Spring length installed - 24.88 inches
Compressed spring - 12.88 inches
Spring compression rate - 300lbs/inch
Gun cradle fluid capacity
Approximately 10.3 gallons
Replenishes 3 purposes
Allows the crew to monitor or the fluid level in the recoil systems
Allows crew to add or draw fluid as necessary
Replenishes the recoil system during firing
Replenisher
Open system, Gravity feed, self venting, translucent plastic Replenisher
Recoil system consists of
Piston, gun cradle, recoil spring and replenisher
Describe Constant recoil
The recoil system provides fixed or constant recoil of 12 inches through all angles of elevation.
Hydro spring
The recoil system uses fluid displacement to absorb recoil energy and spring tension to return the gun to battery.
Concentric
Means that the recoil system and gun tube have a common center
Type of Recoil system
Concentric hydro spring constant recoil system
Phases of function
Manual opening Automatic closing Firing Automatic opening Extraction and ejection
Breech block weight
225 lbs
Breech ring weight
1506 lbs
Bore diameter
4.724 inches
Bore evacuator
28 lbs
Sling point
11 feet 8 inches from the muzzle
Tube weight
2502 lbs
Tube length
17 feet 4 inches
CARC
Chemical agent resistant coating
Condemnation criteria
The gun tube is condemned if the gun tube has fired 1500 EFC rounds or has a 5mm or more of wear into the base metal of the gun tube.
The breech ring is condemned if 4500 EFC rounds have been fired through the breech ring.
Erosion condemnation for gun tube
The cannon tube is condemned when erosion at any location exceeds 5mm in depth
Eccentricity condemnation
Condemn the gun tube if the muzzle shows evidence of an out of round condition that prevents proper bore sighting.
Gun tube cracking condemnation
Condemn if the cracks exceed .125 inch (1/8 inch) on the interior of the gun tube
Condemn if the cracks exceed .250 inch (1/4 inch) on the exterior of the gun tube
Major cause of gun tube wear
Erosion
Pitting criteria
Internal
Zone 1- .03 inch in depth or 20% total surface area
Zone 2- .05 inch in depth or 20% total surface area
Zone 3- ignore pitting in zone 3
External
Unpainted- .02 inch in depth or 80% total surface area
Painted- .04 inch in depth or 80% total surface area
Pitting
Pitting is a result of corrosion on the surface of the gun tube
Cracking
It may be present on the interior or exterior of the gun tube. Cracks will grow progressively worse through continual firing. Characteristics of a crack include feathered edges running in an irregular line with varying width and depth. Cracks may be found anywhere on the external surfaces of the gun tube. Cracks may be found in the bore, bore evacuator, holes or the chamber
Eccentricity
This is the tendency of the gun tube to widen or bell mouth near the muzzle
Erosion
Erosion is a complex phenomenon resulting from extreme chemical reactions under extreme temperatures and pressure which cause an enlarging or damaging of the bore due to firing.
External machined surface
This area contains the surfaces of the cannon that are machined for fitting of external components such as the MRS and the bore evacuator as well as the surfaces that interact with the recoil system.
Inside the bore evacuator
Five evacuator holes equally spaced apart drilled in the gun tube at a 30 degree angle towards the muzzle. The bore evacuator is tested at the factory to sustain 225 psi +/- 5 psi
Type of scavenging system on the M256A1
Eccentric pressure scavenging system
Bore evacuator function
Bore evacuator aids in removing spent gases from the gun tube.
Operation of the chamber and bore
- Initial detonation cartridge case combustion
- Read obturation is provided by the cartridge stub base obturator seal expanding against the rear portion of the chamber region
- Forward obturation by the projectile obturator seal
- Projectile forward movement
- Bore evacuator pressurization
- Shot exit
- Automatic breech opening
- Extraction and ejection begins
- Residual gases evacuated
Recoil system of the M1A2 tank serves four main purposes
- 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
Gun Tube Condemnation
1500 EFC rounds or 5mm wear into the base metal
Breechring condemnation
4500 EFC rounds
Recoil System Exercise
Moving of the piston in the gun cradle to reestablish a fluid film between the packing, seals and sliding surfaces. This prevents dry rotting of the seals and corrosion of the piston surfaces at the packing.
Hydro spring recoil systems inspected and exercised how often
Every 180 days
Methods used to conduct a recoil exercise
M3 oil pump
Firing one round (least preferred method)
Gun mount exercise kit
Borescope frequency of inspection
Every 150 EFC rounds and the first 300 EFC rounds have been fired
Within 180 days prior to firing
When troubleshooting indicates you should
Anytime a cannon is installed even if new
If you are uncertain whether or not a tube has been inspected
Borescope
A borescope is an interior 360 degree visual inspection of the gun tube from the chamber to the muzzle. A borescope is conducted using the M3 borescope device.
