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 WW2 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.

Gun

Mark 1 Original 2 piece barrel
Mark 1/1 Introduced in 1944 with a simplified breech mechanism
Mark 1/2 Introduced in 1945 with a new firing pin unit
Mark 1/3 Obsolete 1960

Carriage

Mark 1 Split trail, wooden wheels, pack carriage
Mark 2 As Mark 1 but 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

Crew

No.1 Detachment Commander
No.2 Breech Operator
No.3 Layer
No.4 Loader
No.5 Ammunition preparation
No.6 Ammunition

There were 3 extra crew when using animal transport

Data

Weight of gun & breech mechanism 451.5 lbs
Weight of the breech section 247 lbs
Weight of the chase section 204.5 lbs
Weight in action 1,856 lb s
Total length of barrel 46.8 inches
Length of bore 43.5 inches
Rifling 28 grooves uniform Right Hand 1/25
Breech mechanism Interrupted screw
Elevation minus 5º to plus 40º
Traverse 20º Left & Right
Recoil system Hydropneumatic variable
Recoil length 17.5 to 35 inches
Length in action 11.1 feet
Width over wheel hubs 4.8 feet

Performance

 

With 20 lb Shrapnel shell
Muzzle velocity 973 feet/second
Maximum range 6,000 yards
 
With 20 lb High Explosive shell (maximum Charge 4)
Muzzle velocity 798 feet/second
Maximum range 4,500 yards

Ammunition

Shell High Explosive 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