Paragraph
Malfunction of gun   ...................................................................................		52
Malfunction of mount   ................................................................................		53

52. MALFUNCTION OF GUN.

a. Fails to Fire; No Percussion on Primer.

Cause		Correction
Broken or weak firing spring. Broken or deformed firing pin.		Remove firing spring retainer, firing spring, and firing pin holder assembly. Replace broken or deformed parts. Clean and lubricate; then replace in breechblock.
Sear not retaining the firing pin in cocked position.		Remove the sear and sear spring. Clean and lubricate; then replace.

b. Fails to Fire Until After Several Percussions on Primer.

Cause		Correction
Percussion mechanism and percussion mechanism release assembly parts not working freely.		Disassemble and examine carefully for burs, or rough surfaces. Smooth with CLOTH, crocus, or an oil stone. Clean, lubricate, and reassemble.
Weak firing spring.		Replace.

c. Fails to Fire When Proper Pressure on Primer is Obtained.

Cause		Correction
Defective primer.		After three percussions, wait 2 minutes before opening breech; then insert another round of ammunition.

d. Fails to Extract Empty Cartridge Case.

Cause		Correction
Broken extractor.		Carefully remove the case by operating from the muzzle end. Examine the edge of the chamber for deformation or burs which might cause difficult extraction. Disassemble mechanism. Replace extractor, if necessary.

e. Misfire.

Cause		Correction
Defective ammunition.		In case of a misfire, at least two or three additional attempts to fire the piece should be made. The breechblock will not be opened until at least 10 minutes after the last unsuccessful attempt to fire the piece. The gun will be kept directed in elevation and traverse either on the target or on a safe place in the field of fire.

f. Breechblock Unable to Be Brought to Full Closed Position.

Cause		Correction
Improper chambering of cartridge case.		Attempt to close the breech. If the breech will not close, open the breech and insert another round. If the malfunction recurs, notify the ordnance maintenance personnel.
Breechblock seized.		Notify ordnance maintenance personnel.

53. MALFUNCTION OF MOUNT.

a. Gun Returns to Battery with Too Great a Shock.

Cause		Correction
Excessive amount of recoil liquid in recuperator cylinder.		Drain and recharge the recuperator cylinder with liquid and air pressure, as described in paragraph 37.
Insufficient amount of liquid in recoil mechanism.		Fill recoil mechanism, as described in paragraph 38.
Recoil mechanism out of order.		Notify ordnance maintenance personnel.

b. Gun Fails to Return to Battery.

Cause		Correction
Excessive friction as stuffing boxes.		Notify ordnance maintenance personnel.
Damaged recoil slides, piston rod, or piston.		Notify ordnance maintenance personnel.
Insufficient amount of liquid and gas pressure in recuperator.		Charge the recuperator with liquid and gas pressure, as described in paragraph 37.
Recoil mechanism out of order.		Notify ordnance maintenance personnel.
Lack of lubrication, or scoring or "freezing" of sliding surfaces.		Notify ordnance maintenance personnel.

c. Spasmodic Counterrecoil.

Cause		Correction
Lack of lubrication or scoring of sliding surfaces.		Notify ordnance maintenance personnel.

d. Gun Recoils More Than the Maximum Distance Allowed.

Cause		Correction
Insufficient amount of liquid and gas pressure in recuperator cylinder.		Charge the recuperator cylinder with liquid and gas pressure, as described in paragraph 37.

e. Gun Slides Out of Battery When Slightly Elevated.

Cause		Correction
Insufficient amount of liquid and gas pressure in recuperator cylinder.		Charge the recuperator cylinder with liquid and gas pressure, as described in paragraph 37. If trouble repeats, notify ordnance maintenance personnel.