|Origin & Designer||[@designer]|
|Crew||6 (Commander, two Gunners, Two Loaders & Driver)|
|Main Armament||1 x 81mm M1 Mortar (Rear Facing)|
|Elevation||-7° to +60°|
|Turret Traverse||60° (Manual)|
|Secondary Armament||1 x .30 cal M1919A4 Machine Gun|
|Ammunition Carried||112 x 81mm + 2000 x .30 cal|
|Combat Weight||7.970 kg|
|Armour||Upper Hull Front: 13mm.|
Lower Hull Front: 6.4mm.
Upper Hull Sides: 6.4mm.
Lower Hull Sides: 6.4mm.
Hull Rear: 6.4mm.
Hull Top: Open.
Hull Bottom: 6.4mm.
|Engine||White 160AX 147 (Petrol)|
|Transmission||4 Forward & 1 Reverse|
|Maximum Road Range||198 miles (320 km)|
|Maximum Cross Country Range||175 miles (282 km)|
|Maximum Water Range||[@maximum_water_range]|
|Maximum Road Speed||45 mph (72 kph)|
|Maximum Cross Country Speed||9 mph (15 kph)|
|Maximum Water Speed||[@maximum_water_speed]|
Year: May 1943
New reinforced Floor to allow for vehicle firing
Year: January 1944
|Notes||Based on the half-track car M2 and built by White, the M4 carried a rear facing 81mm mortar, the mortar also carried a base plate for ground firing, as the weapons was only designed to fire from the vehicle in an emergency. This was changed with the M4A1 which added a strengthened hull to accommodate firing the weapon from the vehicle
The M21 was based on the M3 and had a forward facing 81mm mortar. This allowed for easier firing and to maneuver the vehicle to a new position. The M21 was also built by White with 110 built between January and March 1944 before production was stopped.|