[MarkSheppard]

A completely bizarre USMC project which saw limited combat service:

https://ia800901.us.archive.org/16/i...20Mark%201.PDF

USMC 60-mm mortar T-20 (aka Shoulder Mortar)

MORTAR, 60MM, SHOULDER FIRED

The shoulder fired 60mm Mortar is a development proposed by a member of the Marine Corps. It is of the recoil type, consisting of a 60mm mortar tube partly enveloped by a sleeve containing a spring recoil mechanism which absorbs the recoil and returns the tube to firing position. A trigger activated firing mechanism fires the standard H. E., M49A2 shell with cartridge only, used in this weapon. Recoil of the mortar tube cocks the firing mechanism. The mortar is supported by a bipod with folding legs and has a rectangular shoulder rest attached to the rear end of the sleeve. A bar sight adjustable for elevation by means of a knurled knob is fastened to the left side of the sleeve.

With this mortar it is possible to obtain hits on a 6' x 6' target at ranges up to 600 yards. It is recognized that the heavy recoil of this weapon places a severe strain on the operator.

This weapon was used by the USMC's 1st Division at Peleliu because they had so many failures with Bazooka rockets in the mud of Cape Gloucester

http://www.ibiblio.org/hyperwar/USMC...iu-2.html#fn63

The second new weapon was the 60mm shoulder mortar, a standard mortar adapted to a light machine gun mount for direct, flat-trajectory fire against caves and pillbox openings. Some of its parts proved not rugged enough for sustained use and had to be replaced nearly as often as the poor devils who were obliged to fire the contraption from their shoulders. Essentially its functions duplicated those of the bazooka, and its adoption resulted from the frequent failure of bazooka rockets to detonate in the soft mud of Cape Gloucester. However, there proved to be very little soft ground amid the coral of Peleliu and, although the shoulder mortar was used effectively, it came to be considered less practical all around than the weapon it had been designed to replace.63

63. "As presently constructed, they (shoulder mortars) are too heavy and certain parts are too weak. . . . After firing two to four rounds, it is necessary to replace the gunner. Units feel that the shoulder mortar as now constructed is not of sufficient value to include it in the authorized weapons." 1st MarDiv SAR, II, Annex A, 5.