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

M60 7.62mm Machine Guns (All Versions)

The current crop of rifle caliber machine guns after the Korean War were all John M. Browning designs: the M1917A1 heavy water-cooled; the M1919A4 medium air-cooled; and the M1919A6 light air-cooled.  The Army wanted a new general purpose machine gun (GPMG) that was lighter than the lightest Browning (M1919A6); 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 MG42 general purpose machine gun 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 (7.62x63mm) 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 MG42.  The result was the M60 machine gun in 7.62mm NATO. 

The M60 GPMG has several design features shared with the MG42: The M60 infantry gun has a butt stock and pistol grip/trigger group.  The M60 has a combination hand guard and barrel shroud instead of the slotted barrel jacket of the MG42.  The M60 has a folding bipod similar to the MG42 design and is adapted to a tripod mount.

The basic M60 machine gun as used by all services in Vietnam. (Photo: U.S. Ordnance, Inc.)
A modified M60B (unofficial designation) “free gun” as used by the door gunners of Light Attack Helicopter Squadron THREE [HA(L)-3]. Gunners would attach themselves to the airframe with their gunner’s safety belts and hang out the door firing these guns to protect the belly and tail of the UH-1 when suppressing ground fire. This particular gun has a mechanical buffer fitted to boost its rate of fire. The buttstock of the ground gun has been replaced by the sheet metal cover from a M60C. The bipod has been removed from the barrel and a second pistol grip fitted to the forearm. Extra springs have been added to the inside of the feed cover to help draw the belt. On some guns, the forearm was removed and the pistol grip was attached to the operating rod cylinder. In action, the gunner flipped the gun on its side so that the belt draped over the feed cover and the links and brass ejected downward. (Photo: www.seawolves.org)

The M60C was a helicopter machine gun.  The butt stock and pistol grip of the M60 ground gun were removed.  The butt stock was replaced by a sheet metal cover.  The pistol grip was replaced by a solenoid-actuated trigger.  The hand guard/barrel shroud was removed as was the bipod from the barrel.  The M60C 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. The M60C 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.

M60C -- The M60C was the aircraft fixed gun version of the basic M60. This was the gun carried on early UH-1 gunship helicopters and by the OV-10 "Bronco" aircraft used by the Navy's famous "Black Ponies" [VA(L)-4]. The photo shows the M6/XM21 armament mockup for a UH-1 helicopter. This is a composite photo which shows the twin M60C mountings in the background (M6) and the M134 mini-gun mounting (XM21 – later standardized as M21) in the foreground. In reality, the UH-1 carried either two sets of twin M60C guns or two M134 Mini-guns, but never a composite of both. The M60C gun had a mechanical buffer to increase its rate of fire and was fired by a solenoid trigger similar to the M60E2. The M6 armament system also accommodated a 7-round 2.75-inch rocket pod similar to that shown mounted on the XM21 mockup. The pod was not attached to the M6 mockup in this photo. (Photo: US Army)

The M60D was a flexible gun used by special operations units or helicopters. The butt stock was replaced by a pair of spade grips (similar to the .50 Browning MG). A trigger bar connected the triggers to the trigger group that replaced the pistol grip/trigger group of the M60. Barrels may or may not have bipods. Aircraft guns were fed through a flexible feed chute that attached to the side of the gun. The cradle of the aircraft gun incorporates a bag to catch expended links and brass as they ejected from the gun during firing. In Viet Nam, Mobile Support Team TWO users clipped a C-ration can to 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.

M60D -- The M60D was the flexible version of the M60 for use by aircrew and by MST-2. The gun was considerably lightened by removing the forearm. A simple ring sight replaced the rear leaf sight of the M60, the pistol grip was removed and replaced with spade grips. The trigger was relocated to the spade grip assembly. Here, two M60D guns are installed on a LSSC belonging to the MST-2 detachment based at Nha Be in 1969. Notice the C-ration cans clipped to the guns to help feed the ammunition belt. This was a common practice in Viet Nam. Where armament was placed on a boat and how its ammunition was fed to the gun varied from boat to boat and detachment to detachment in MST. These former 20mm ammunition cans have been salvaged to hold continuous linked belts of 7.62mm for the guns. On our two LSSC at SEA FLOAT/SOLID ANCHOR we used scrounged UH-1 gunship ammunition boxes. (Photo: Terry Knott)

The M60 is a general purpose machine gun 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 per minute. Other versions of the basic M60 are the M60E1, M60E2, M60E3, and Mk 43 Mod 0 (aka M60E4).

The M60 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 M60 was made by the M60E1.

The M60E1 was a redesign of the M60 to cure in-service problems of the various users. The new M60E1 revised the top cover to allow it to be closed when the gun was not cocked and the bolt was forward. The M60 could be damaged if someone attempted to close the cover on an uncocked gun. The M60E1 modified the bipod and moved it from the barrel to the gas cylinder. The carrying handle was removed from the M60 receiver and permanently attached to the barrel on the M60E1. The barrels of the M60 and M60E1 were not interchangeable; the M60 barrel incorporated the gas cylinder with the barrel and the M60E1 moved the gas cylinder to permanently attach it to the receiver. The forearm of the M60E1 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 M60E3 which was standardized.

M60E1 -- the M60E1 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 M60 to the gas cylinder on the M60E1. The carrying handle has been moved from the receiver of the M60 and permanently attached to the modified barrel of the M60E1. The top of the forearm has been removed on the M60E1 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 M60. The M60E1 was not put into series production. (Photo: US Army)

The M60E2 is a co-axial machine gun mounted in armored vehicles, most notably the M1 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 M60C, the gun is fired by a solenoid. Unlike the M60C, the M60E2 has a manual trigger in case the solenoid fails. Weight is about 18 pounds.

M60E2 -- This is the M60E2 as found on the M1 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)

The M60E3 is now standard with US Army, Navy, Air Force, and Coast Guard units. It has been replaced in the Marine Corps by the M240G and, with minor modifications, in the US Army by the M240B. (The M240 is a version of the Belgian MAG58 built by Fabrique Nationale of Herstal, Belgium, and has the boxy-receiver appearance of the old Browning .30 caliber M1919 series. The M240 is gas-operated and uses the same belted ammunition as the M60.) The M60E3 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 M60E1. Weight is about 19 pounds.

M60E3 -- The M60E3 is the current version of the venerable M60. It uses a modified butt stock, forearm, adds a second pistol grip, relocates the bipod to the gas cylinder (like the M60E1) and a modified barrel with attached carrying handle to assist barrel removal. Like the M60E1 predecessor, the feed cover can be closed when the gun is not cocked (bolt forward).(Photo: U.S. Ordnance, Inc.)

M60E3 Conversion Kit FOR 7.62mm Machine Gun M60

These parts convert an M60 to the product improved M60E3. Compare these parts with those of the Mk 43 Mod 0 (M60E4) for design differences. Both M60E3/Mk 43 Mod 0/M60E4 barrels have an attached carrying handle to assist the barrel’s removal. Like the M60E1 predecessor, the feed covers of these product-improved guns can be closed when the gun is not cocked (bolt forward). (Photo: U.S. Ordnance, Inc.)
The Fabrique-Nationale M240G 7.62mm NATO machine gun of the USMC. This gun is replacing the M60 GPMG in all Marine Corps units on an attrition basis. The Army M240B is very similar. (Photo: USMC)

The Mk 43 Mod 0 is a modification of the basic M60E3 for Naval Special Warfare operators. Naval Sea Systems Command (NavSeaSysCom) at NAD Crane, Indiana, is responsible for the Mk 43 Mod 0. The Mk 43 retains the previous modifications of the M60E3 and the second pistol grip integrated into the forearm. The gas system is modified and a new lighter and 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 M60 but eliminates over 5 pounds of weight. The reduced weight and length give the NSW operator more agility on the battlefield. Army special operations units call this gun the M60E4.

MK 43 Mod 0 (M60e4)

Mk 43 Mod 0 (aka M60E4) -- Naval Sea Systems Command (NavSeaSysCom), at NAD Crane, Indiana is producing the Mk 43 Mod 0 version of the M60E3 for naval special operations units. This is a modified gun that lightens the M60E3 even more while retaining its firepower. (Photo: U.S. Ordnance, Inc.)

MK43 Mod 0 (M60E4) Conversion Kit FOR 7.62mm Machine Gun M60

These are the parts that are used to convert a stock M60 into the Mk 43 Mod 0 (M60E4). The basic M60 receiver is retained, but it has been strengthened to resist the “stretching” or lengthening that affected the reliability of Viet Nam-era guns. Barrels are Stellite®-lined and chrome plated for longevity. Notice the shorter barrel, flash suppressor, and modified gas cylinder that distinguishes this model. Like other product-improved M60-series guns, the operating rod has a second sear notch to prevent a run away (uncontrolled) gun whereby the gun continues to fire when the trigger is released. (Photo: U.S. Ordnance, Inc.)

As this is written, NAD Crane has announced two new programs to replace the M60E3 and Mk 43 Mod 0 (M60E4) guns within the Naval Special Operations community. These guns are based on the Fabrique Nationale-designed M249 5.56mm squad automatic weapon used by the US Army and Marine Corps. The new weapons are designated Mk 46 Mod 0 for the 5.56mm SAW and Mk 48 Mod 0 for the 7.62mm SAW. The Mk 46 will use the belted ammunition of its M249 brother. The M48 will use the belted ammunition of the M60-series guns it replaces.

The new NAD Crane Mk 46 Mod 0 machine gun in 5.56mm NATO caliber has the Picatinny rail integration (mounting) system or RIS installed for various sighting options of the using operator – red dot sights, night vision devices, laser designators, etc. It is belt-fed only and has a cyclic rate of 750 rounds per minute. The Picatinny RIS fitted to the forearm or hand guard allows the operator increased flexibility for the mounting of the new sighting devices. The barrel is lighter and shorter than that of its M249 brother. (Photo: www.World.Guns. Ru)
The new NAD Crane Mk 48 Mod 0 machine gun in 7.62mm NATO caliber has the Picatinny RIS installed like the Mk 46 In this photo, a red dot sight is mounted to the top cover of the gun and a second hand grip is mounted to the forearm. The Mk 48 is 17 percent lighter than the M240G used by the USMC or M240B used by the Army. Cyclic rate is 700 rounds per minute. (Photo: www.World.Guns. Ru)

© 2005 Bob Stoner R5