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Ordnance Notes -- by Bob Stoner GMCM(SW) Ret.

M-60 7.62mm Machineguns (including M-60D versions)


Photo: US Army
The basic M-60 machinegun as used by all services in Vietnam. (More photos below.)

The current crop of rifle caliber machineguns after the Korean war were all John M. Browning designs: the M-1917A1 heavy water-cooled; the M-1919A4 medium air-cooled; and the M-1919A6 light air-cooled.  The Army wanted a new general purpose machinegun (GPMG) that was lighter than the lightest Browning (M-1919A6); had a quick-change barrel (which the Browning did not); could be used as an infantry, vehicular, or aircraft gun; had an improved belt feed, and could be fired from either the shoulder, hip, bipod, or tripod. 

Army Ordnance experimented with a T-series copy of the German MG-42 general purpose machinegun in the mid-1940s.  Ordnance even manufactured copies in .30 caliber.  However, someone fouled-up the reverse engineering and made the receiver too short to accommodate the extra length of the American .30 caliber cartridge vs. the German 7.92x57mm cartridge.  The American replicas would not function and the project was abandoned at the end of 1945. 

Ordnance did not give up and decided to incorporate features of several guns from its previous research.  The new GPMG would use a modification of the American WW1 Lewis Gun gas and bolt system and the feed mechanism of the German WW2 MG-42.  The result was the M-60 machine gun in 7.62mm NATO. 

The M-60 GPMG has several design features shared with the MG-42: The M-60 infantry gun has a butt stock and pistol grip/trigger group.  The M-60 has a combination hand guard and barrel shroud instead of the slotted barrel jacket of the MG-42.  The M-60 has a folding bipod similar to the MG-42 design and is adapted to a tripod mount.

The M-60C is a helicopter machinegun.  The butt stock and pistol grip of the M-60 ground gun are removed.  The butt stock is replaced by a sheet metal cover.  The pistol grip is replaced by a solenoid-actuated trigger.  The hand guard/barrel shroud is removed as is the bipod from the barrel.  The M-60C was mounted in two gun pairs on either side of UH-1 helicopters.  The pairs of guns were slaved to the pilot's lead-computing sight.  A mechanical buffer replaces the hydraulic buffer.  The mechanical buffer raises the gun's cyclic rate of fire.cyclic rate of fire. The M-60C is also used in pairs as part of the M-6 armament system on UH-1 helicopters (see below) and in the fuselage sponsons of OV-10 "Bronco" aircraft as used by Navy Light Attack Squadron FOUR [VA(L)-4] in Viet Nam.

The M-60D is a flexible gun used by special operations units or helicopters. The butt stock is replaced by a pair of spade grips (similar o the .50 Browning MG). A trigger bar connects the triggers to the trigger group that replaces the pistol grip/trigger group of the M-60. Barrels may or may not have bipods. Aircraft guns are fed through a flexible feed chute that attaches to the side of the gun. The cradle of the aircraft gun incorporates a bag to catch expended links and brass as they are ejected from the gun during firing. In Viet Nam, MST users clipped a C-ration can o the bracket that was designed to hold the ammunition bandolier. The purpose of the C-ration can was to help the gun feed the ammunition more reliably.

The M-60 is a general purpose machinegun that weighs 23 pounds, is air-cooled, gas operated, belt-fed, and fires full automatic. Length is approximately 43 inches. Cyclic rate is approximately 550 to 650
rounds/minute.

Other versions of the basic M-60 are the M-60E1, M-60E2, M-60E3, and Mk 43 Mod 0.

The M-60 has several quirks that caused users problems over the years. The barrel change lever could not be worked without asbestos gloves. Several important parts can be installed wrong which either render the gun
inoperable or a single shot weapon. For instance, it was found that the mechanical buffer would stretch the gun's receiver if used for extended periods. The first attempt to cure the problems identified in the M-60 was made by the M-60E1.

The M-60E1 was a redesign of the M-60 to cure in-service problems of the various users. The new M-60E1 had a revised top cover that allows it to be closed when the gun is not cocked and the bolt is forward. The M-60 could be damaged if someone attempted to close the cover on an uncocked gun. The M-60E1 modified the bipod and moved it from the barrel to the gas cylinder. The carrying handle was removed from the M-60 receiver and permanently attached to the barrel on the M-60E1. The barrels of the M-60 and M-60E1 were not interchangeable; the M-60 barrel incorporated the gas cylinder with the barrel and the M-60E1 moved the gas cylinder to permanently attach it to the receiver. The forearm of the M-60E1 was modified by removing the top to allow easier changing of a hot barrel. The gun was not put into production, but the design innovations it pioneered were incorporated into the M-60E3 which was standardized.

The M-60E2 is a co-axial machinegun mounted in armored vehicles, most notably the M-1 Abrams tank. It has an extended barrel and gas cylinder to exhaust the gun gas outside the turret of the tank and keep it out of the interior. Like the M-60C, the gun is fired by a solenoid. Unlike the M-60C, the M-60E2 has a manual trigger in case the solenoid fails. Weight is about 18 pounds.

The M-60E3 is now standard with US Army, Navy, Air Force, and Coast Guard units. It has been replaced in the Marine Corps by the M-240G. (The M-240G is a version of the Belgian MAG-58 built by Fabrique Nationale and has the boxy-receiver appearance of the old Browning .30 caliber M-1919 series. The M-240G is gas-operated and uses the same belted ammunition as the M-60.) The M-60E3 has a simplified butt stock, a modified and lightened forearm, a second pistol grip, a modified barrel with a permanently attached carrying handle and lightened, shorter flash suppressor. A lightened and modified bipod is attached to the gas cylinder as in the M-60E1. Weight is about 19 pounds.

The Mk 43 Mod 0 is a modification of the basic M-60E3 for naval special warfare operators. Naval Sea Systems Command (NavSeaSysCom) at NAD Crane, IN is responsible for the Mk 43 Mod 0. The Mk 43 retains the previous modifications of the M-60E3 and the second pistol grip, but eliminates the forearm. The gas system is modified and a new, fluted, shorter barrel is fitted. (The barrel is only slightly longer than the gas cylinder.) The
flash suppressor has been modified to be more efficient with the shorter barrel. The Mk 43 retains the firepower of the M-60 but eliminates over 6 pounds of weight. The reduced weight and length give the NSW operator more
agility on the battlefield.

Photos


Photo: US Army
M60E1 -- the M-60E1 was the first attempt to improve several problems that were identified
with the gun. Note that the bipod has been changed and moved from the barrel on the M-60 to
the gas cylinder on the M-60E1. The carrying handle has been moved from the receiver of the
M-60 and permanently attached to the modified barrel of the M-60E1. The top of the forearm
has been removed on the M-60E1 to assist quick barrel changes. Not shown are the
modifications that allow the cover to be closed when the bolt is forward; something that cannot
be done on the M-60. The M-60E1 was not put into series production.


Photo: US Army
M60E2 -- This is the M-60E2 as found on the M-1 series Abrams tank.
Note the extended barrel and gas cylinder to vent gases outside the
interior of the turret. The cocking handle is the ring-shaped object at the
rear of the receiver. No stock, pistol grip or forearm is used on this gun.
The cylinder below the belt feed opening is the firing solenoid; its manual
back-up firing lever is immediately to its rear.


Photo: US Army
M60E3 -- The M-60E3 is the current version of the venerable M-60. It uses a
modified butt stock, forearm, adds a second pistol grip, relocates the bipod
to the gas cylinder (like the M-60E1) and a modified barrel with attached
carrying handle to assist barrel removal. Like the M-60E1 predecessor, the
feed cover can be closed when the gun is not cocked (bolt forward).


Photo: US Army
Naval Sea Systems Command (NavSeaSysCom), at NAD Crane, Indiana is
producing the Mk 43 Mod 0 version of the M-60E3 for naval special operations
units. This is a modified gun that lightens the M-60E3 even more while retaining
its firepower.


Photo: US Army
M60C -- The M-60C is the aircraft fixed gun version of the basic M-60.
This is the gun carried on early UH-1 gunship helicopters and by the OV-10
"Bronco" aircraft used by the Navy's famous "Black Ponies" (VAL-4). The
photo shows the M-6/XM-21 armament set-up for a UH-1 helicopter. This is a
composite photo which shows the twin M-60C mountings in the background (M-6)
and the M-134 mini-gun mounting (XM-21) in the foreground. In reality, the
UH-1 carried either two sets of twin M-60C guns or two M-134 mini-guns, but
never a composite of both. The M-60C gun had a mechanical buffer to
increase its rate of fire and was fired by a solenoid trigger similar to the
M-60E2.



M60D -- The M-60D was the flexible version of the M-60 for use by aircrew
and by MST. The gun was considerably lightened by removing the forearm. A
simple ring sight replaced the rear leaf sight of the M-60, the pistol grip
was removed and replaced with spade grips. The trigger was relocated to the
spade grip assembly.

R-1

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2002 Bob Stoner