3.7 inch Mountain Howitzer

3.7 inch How


Introduced, officially, in February 1917 the gun broke down into several loads for either man or mule packing. The barrel was in two halves joined by a junction nut. Used during World War 2 mainly in the Far East and Italy, it equipped the mountain batteries and was also used by the airborne artillery until replaced by the US 75 mm Howitzer. It was not declared obsolete until 1960.




Mark 1  
Mark 1/1 Introduced 1944 with simplified breech mechanism
Mark 1/2 Introduced 1945, new firing pin unit
Mark 1/3 Obsolete 1960




Mark 1 Split trail, wooden wheels, pack carriage
Mark 2 As Mark 1 with fittings for animal draught
Mark 3 As Mark 2 but with fixed spades
Mark 4P Pneumatic tyred
Mark 5 Light version for airborne use




No.1 Detachment Commander
No.2 Breech Operator
No.3 Layer – fires gun
No.4 Loader
No.5 Ammunition
No.6 Ammunition




Weight of gun & breech mechanism 451.5 lbs
Weight of breech section 247 lbs
Weight of chase section 204.5 lbs
Weight in action 1,856 lbs
Total length 46.8 inches
Length of bore 43.5 inches
Rifling 28 grooves uniform right hand 1/25
Breech mechanism Interrupted screw
Elevation -5º to +40º
Traverse 20º left & right
Recoil system Hydropneumatic variable
Recoil length 17.5 to 35 inches




With 20 lb Shrapnel shell:  
Muzzle velocity 973 feet/second
Maximum range 6,000 yards
With 20 lb HE shell (max Charge 4):  
Muzzle velocity 798 feet/second
Maximum range 4,500 yards




Shell HE Mark 3 Amatol filled. Restricted to charge 4 or less
Shell Shrapnel Mark 6 Nose ejecting filled with lead/antimony bullets
Shell Smoke Bursting Mark 3 White phosphorus filled
Shell Smoke Base Ejection Mark 1 Rarely seen
Shell Star Mark 3 Star unit & parachute with Fuze Time & Percussion No 221T
Shell HEAT Mark 1 Developed 1942
Propelling Charge  
5 part in 3.6 inch long brass case