Carrier, 81mm Mortar, Half-Track, M21

Overview

Carrier, 81mm Mortar, Half-Track, M21
General Data
Type	Self-Propelled Mortar
Place of Origin	United States of America
Manufacturer	White Motor Company
Produced	Jan 1944 - Mar 1944
Number Built	110
In Service	1944 - ?
Development
Chassis	Carrier, Personnel, Half-Track, M3
Developed From	Carrier, 81mm Mortar, Half-Track, T19
Armament
Main Gun	Mortar, 81mm, M1 in Mount, Mortar: 81mm, M4 (without baseplate) (97-rnds)
Pintle / AA Gun	12.7x99mm Machine Gun, Caliber .50, HB, M2, Flexible (400-rnds)
Crew Weaponry	1 x .45 ACP Submachine Gun, Caliber .45, M1 (600-rnds) 6 x Rocket, 2.36-inch: HEAT, M6 12 x Grenade, Fragmentation, Hand, Mk. II 12 x Mine, Antitank, M1A1
Misc Specs
Crew	6
Dimensions
Weight	9,072kg
Length	6.007m (Roller) 6.22m (Winch)
Width	2.216m
Height	2.21m
Tread	1.621m
Wheelbase	3.442m
Automotive
Engine	White 160AX I-6, liquid-cooled 6325.4cm² gasoline (72-octane) 150 HP @ 3,000 rpm
Ground Clearance	0.432m
Fuel Capacity	227.1 liters (72-octane)
Operational Range	~321.9km
Maximum Fording Depth	0.813m
Minimum Turning Diameter	18.288m

The Carrier, 81mm Mortar, Half-Track, M21 is an American self-propelled mortar developed in the 1940s by combining the Carrier, Personnel, Half-Track, M3 and the Mortar, 81mm, M1.

Development

On 7 June 1943, OCM 20846 standardized the prototype Carrier, 81mm Mortar, Half-Track, T19 as Carrier, 81mm Mortar, Half-Track, M21, allowing the vehicle to enter standard service.

Production began by the White Motor Company in January 1944, and ending in March 1944 with 110 vehicles being manufactured during that period. Late production vehicles can be identified by rod-type side stowage racks.

Description

The Carrier, 81mm Mortar, Half-Track, M21 is essentially the Carrier, Personnel, Half-Track, M3 but with the rear compartment modified to fit the Mortar, 81mm, M1. The mortar is installed onto the usual Mount, Mortar: 81mm, M4 but with the baseplate installed in the rear compartment of the vehicle.

The mortar is installed to fire forward, unlike the M4 and M4A1 mortar carriers which fire rearwards.

Variants

Carrier, Personnel, Half-Track, M3 Standard model. Carrier, Personnel, Half-Track, M3E1 Experimental model. Carrier, Personnel, Half-Track, M3E2 Experimental model, became M5. Carrier, Personnel, Half-Track, M3A1 Updated model. Derivatives Carrier, Personnel, Half-Track, M5 Alternate model, derived from M3E2. Carriage, Motor, 40mm Gun, M34 Model mounting a single 40mm on the rear deck. Carriage, Motor, 40mm Gun, T54 Model mounting a single 40mm M1 on the rear deck. Carriage, Motor, 40mm Gun, T54E1 T54E1, but armoured. Carriage, Motor, 40mm Gun, T59 T54, but with equipment tailored to work in tandem with the Carrier, Instrument, T18. Carriage, Motor, 40mm Gun, T59E1 T59, but armoured. Carriage, Motor, 40mm Gun, T60 T54E1 with two out-board .50 caliber machine guns. Carriage, Motor, 40mm Gun, T60E1 T60 with alternate armour layout. Carriage, Motor, 75mm Howitzer, T30 Model fitting a 75mm howitzer. Carriage, Motor, 105mm Howitzer, T19 Model fitting a 105mm howitzer. Carriage, Motor, 105mm Howitzer, T38 Proposed model fitting a 105mm M3 Howitzer. Carriage, Motor, Combination Gun, M15 Model derived from T28E1 but with additional armour and new machine guns. Carriage, Motor, Combination Gun, M15A1 M15 but with weapons re-positioned and an updated 37mm gun. Carriage, Motor, Combination Gun, T28E1 Prototype model with 37mm gun and two out-board water-cooled .50 caliber machine guns. Carriage, Motor, Multiple Gun, M13 Model fitting twin .50 caliber machine guns in a M33 mount on the rear deck. Carriage, Motor, Multiple Gun, M16 Model fitting quad .50 caliber machine guns in a M45D mount on the rear deck. Carriage, Motor, Multiple Gun, M16A1 Model fitting quad .50 caliber machine guns in a M45F mount on the rear deck. Carriage, Motor, Multiple Gun, M16A2 Model fitting quad .50 caliber machine guns in a M45F mount on the rear deck, conversion from existing M16 or M3. Carriage, Motor, Multiple Gun, T1E4 Prototype model fitting twin .50 caliber machine guns. Became the Carriage, Motor, Multiple Gun, M13. Carriage, Motor, Multiple Gun, T37 Prototype model fitting quad .50 caliber machine guns in a T60 mount on the rear deck. Carriage, Motor, Multiple Gun, T37E1 Prototype model fitting quad .50 caliber machine guns in a T60E1 mount on the rear deck. Carriage, Motor, Twin 20mm Gun, T10E1 Model fitting twin 20mm guns in a turret on the rear deck. Carriage, Motor, Twin 40mm Gun, T68 Model fitting twin 40mm guns in an elaborate mount on the rear deck. Carrier, 81mm Mortar, Half-Track, M4 Model fitting a rear-facing Mortar, 81mm, M1. Carrier, 81mm Mortar, Half-Track, M4A1 Model fitting a rear-facing Mortar, 81mm, M1. Carrier, 81mm Mortar, Half-Track, M21 Model fitting a forward-facing Mortar, 81mm, M1. Carrier, 81mm Mortar, Half-Track, T19 Prototype model fitting a forward-facing Mortar, 81mm, M1. Became the Carrier, 81mm Mortar, Half-Track, M21.

United States of America Land Vehicles Interwar & World War II Period (1919 — 1945)

Wheeled Vehicles
Combat Vehicles	Armoured Cars	T17 (E1 • E2 • E3) • T18 M8
	Scout Cars	T6 • T7 • T8 • T9 • T10 • T11 (E1 • E2) • T24 • T25 (E1 • E2 • E3) M3 • (A1)
	Gun Motor Carriages (GMC)	M6 • T66 • T55 (E1)
	Multiple Gun Motor Carriage (MGMC)	T69
Utility	Transport & Towing	M20
	Trailers	M15 Trailer

Sources
Books	Online	Documents
• Half-Track — A History of American Semi-Tracked Vehicles, R.P. Hunnicutt, 2001 (ISBN 0-89141-742-7)		• TM 9-710 — Basic Half-Track Vehicles (White, Autocar, Diamond T), 1944-02-23 • TM 9-3071-1 — 60-mm Mortars M2 and M19; 60-mm Mortar Mount M5; 60-mm Mortar Baseplate M1; 81-mm Mortars M1 and M29; and 81-mm Mortar and Mounts M4, M23A1, M23A2, and M23A3, 1967-01-12