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.
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The
basic M60 machine gun as
used by all services in Vietnam. (Photo: U.S.
Ordnance, Inc.) |
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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 The buttstock of the ground gun has been
replaced by the sheet metal cover from a M60C.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.
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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.
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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.
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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.
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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.
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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.)
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M60E3 Conversion
Kit FOR 7.62mm Machine Gun M60 |
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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.) |
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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.
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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.)
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MK43
Mod 0 (M60E4) Conversion Kit FOR 7.62mm Machine Gun M60 |
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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.)
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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.
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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) |
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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
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