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As well as an offensive load of 4000 Ibs of bombs, the
eight mounted nose guns and three guns in each wing with a total of 4000 rounds and four turret guns with 500 rpg, the
A/B-26 Invader was a formidable adversary, but development of the new and much modified B-26K gave the Invader a further
edge in aerial combat and allowed this old and tired aircraft to continue to operate through the Second and Korean wars to
continue through Vietnam.
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Eight mounted nose guns
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Three guns in each wing
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Four turret guns ( Two remote turrets )
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4000 Ibs of bombs
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The A-26A (B-26K) could carry a maximum of 800 pounds
underneath the wings plus 4000 pounds internally. However, the actual load carried on combat missions was usually somewhat
less in order to gain maneuverability and to reduce stress loads.
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A typical underwing load consisted of a pair of SUU-025
flare dispensers Two LAU-3A rocket pods, and four CBU-14 cluster bomb units.
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Later, the rockets and flares were often replaced by
500 lb BLU-23 or 750 lb BLU-37 finned napalm bombs.
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The M31 and M32 incendiary clusters could also be carried,
as well as M34 and M35 incendiary bombs
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M1A4 fragmentation clusters, M47 white phosphorus bombs,
and CBU-24, -25, -29, and -49 cluster bomb units.
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General-purpose bombs such as the 250-lb MK-81, the
500-lb MK-82, and 750-lb M117 could also be carried.
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During the Korean war alone, Invaders flew some 60,000
sorties Invaders were credited with the destruction of 38,500 enemy vehicles, 3700 railway cars, 406 locomotives,
and seven aircraft.
The M2 Machine Gun
The Browning .50 Caliber Machine Gun is a heavy machine gun designed towards the
end of World War I by John Browning. It was nicknamed "Ma Deuce" by US troops or simply called "fifty-cal."
in reference to its caliber. The design has had many specific designations; the official designation for the current infantry
type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly-armored vehicles
and boats, light fortifications, and low-flying aircraft.
The Browning .50 caliber machine gun has been used extensively as a
vehicle weapon and for aircraft armament by the United States from the 1920s to the present day. It was heavily used
during World War II, the Korean War, the Vietnam War, as well as during operations in Iraq in
the 1990s and 2000s. It is the primary heavy machine gun of NATO countries, and has been used by many other countries.
It is still in use today, with only a few modern improvements. The M2 has been in use longer than any other small arm
in U.S. inventory. It was very similar in design to the smaller Browning Model 1919 machine gun.
History
A variant without a water jacket, but with a thicker-walled, air-cooled
barrel superseded it (air-cooled barrels had already been used on variants for use on aircraft, but these quickly overheated
in ground use). This new variant was then designated the M2 HB ("HB" for "Heavy Barrel"). The added mass
and surface area of the new barrel compensated, somewhat, for the loss of water-cooling, while reducing bulk and weight (the
M2 weighed convert|121|lb|abbr=on, with water, whereas the M2 HB weighs 84 lb). Due to the long procedure for
changing the barrel, an improved system was developed called QCB (quick change barrel). A lightweight version, weighing
24 lb (11 kg) less—a mere 60 lb (27 kg)—was also developed
Design details
The M2 is a scaled-up version of John Browning's M1917 .30 caliber
machine gun (even using the same timing gauges), fires the .50 BMG cartridge, which today is also used in high-powered sniper
rifles and long range target rifles due to its excellent long range accuracy, external ballistics performance,
incredible stopping power, and lethality. The M2 is an air-cooled, belt-fed, machine gun that fires from a closed
bolt, operated on the short recoil principle. In this action, the bolt and barrel are initially locked together,
and recoil upon firing. After a short distance, the bolt and barrel unlock, and the bolt continues to move rearwards relative
to the barrel. This action opens the bolt, and pulls the belt of ammunition through the weapon, readying it to fire again,
all at a cyclic rate of 450–600 rounds per minute (600–1,200 M2/M3 in WW2 aircraft, 300 synchronized M2). This
is a rate of fire not generally achieved in use, as sustained fire at that rate will "shoot out" the barrel within a few thousand
rounds, necessitating replacement. The M2 machine gun's sustained rate of fire is considered to be anything less than 40 rounds
per minute.
The M2 has a maximum range of 7.4 kilometers (4.55 miles), with a maximum
effective range of 1.8 kilometers (1.2 miles) when fired from the M3 tripod. In its ground-portable, crew-served role,
the gun itself weighs in at a hefty 84 pounds (38 kg), and the assembled M3 tripod another 44 pounds (20 kg). In this configuration,
the V-shaped "butterfly" trigger is located at the very rear of the weapon, with a "spade handle" hand-grip on either side
of it and the bolt release the center. The "spade handles" are gripped and the butterfly trigger is depressed with one or
both thumbs. When the bolt release is locked down by the bolt latch release lock on the buffer tube sleeve, the gun functions
in fully automatic mode. Otherwise, the M2 is a single-shot weapon. Unlike virtually all other modern machine guns, it has
no safety. Conversely, the bolt release can be unlocked into the up position resulting in single-shot firing (the gunner must
press the bolt latch release to send the bolt forward). In either mode the gun is fired by pressing the butterfly triggers.
Recently new rear buffer assemblies have used squeeze triggers mounted to the hand grips, doing away with the butterfly triggers.
Because the M2 was intentionally designed to be fit into many configurations,
it can be adapted to feed from the left or right side of the weapon by exchanging the belt-holding pawls, the belt feed pawl,
and the front and rear cartridge stops, then reversing the bolt switch. The conversion can be completed in under a minute
with no tools.
There are several different types of ammunition used in the M2HB, including
the current types: M33 Ball (706.7 grain) for personnel and light material targets, M17 tracer, M8 API (622.5 grain), M20
API-T (619 grain), and M962 SLAP-T. The latter ammunition along with the M903 SLAP (Saboted Light Armor Penetrator) round
can penetrate up to 3/4 inch armor at 1500 meters. This is achieved by using a .30 inch diameter tungsten penetrator. The
SLAP-T adds a tracer charge to the base of the ammunition. This ammunition was type classified in 1993.
When firing blanks, a large blank-firing adapter (BFA) must
be used to keep the gas pressure high enough to allow the action to cycle. The adapter is very distinctive, attaching to the
muzzle with three rods extending back to the base. The BFA can often be seen on M2s during peacetime operations.
Combat use
The M2 .50 Browning machine gun has been used for various roles:
*
A medium infantry support weapon
* As an anti-aircraft gun in some ships, or on the ground. The original water-cooled
version of the M2 was used as an emplaced or vehicle-mounted anti-aircraft weapon on a sturdy pedestal mount. In some cases
multiple air and water-cooled weapons were grouped. In some of these instances the mount featured one M2 with a left-handed
feed and one with right-handed feed are paired. Four and six guns are also sometimes mounted on the same turret.
* Primary
or secondary weapon on an armored fighting vehicle.
* Primary or secondary weapon on a naval patrol boat.
* Secondary
weapon for anti-boat defense on large naval vessels (corvettes, frigates, destroyers, cruisers, etc).
* Coaxial gun
or independent mounting in some tanks.
* Fixed-mounted primary armament in World War II-era U.S. aircraft such as the P-47
Thunderbolt, P-51 Mustang, and the Korean-era U.S. F-86 Sabre.
* Fixed or flexible-mounted defensive
armament in World War II-era bombers such as the A-26 Invader, B-17 Flying Fortress, and B-24 Liberator.
United States
At the outbreak of the Second World War the United States had versions
of the M2 in service primarily as fixed aircraft guns and as anti-aircraft weapons (mounted on and off a wide variety of vehicles
and ships). It was also technically still in service as an anti-tank weapon, as originally intended. On most of the vehicles
the weapon was mounted on it was placed in a position designed for anti-aircraft rather than any other use. Units in the field
often modified the mountings on their vehicles, especially tanks and tank destroyers, to be more useful in the anti-personnel
role. Reports vary on its effectiveness in this role. There are instances of reports about the "essential" nature of the weapon
for anti-personnel uses.
M2 variants
The basic M2 was deployed in US service in a number of subvariants,
all with separate complete designations as per the US Army system. The basic designation as mentioned in the introduction
is Browning Machine Gun, Cal. .50, M2, with others as described below.
The development of the M1921 water-cooled machine gun which led to
the M2, meant that the initial M2s were in fact water-cooled. These weapons were designated Browning Machine Gun, Cal.
.50, M2, Water-Cooled, Flexible. There was no fixed water-cooled version.
Improved air-cooled heavy barrel versions came in three subtypes. The
basic infantry model, Browning Machine Gun, Cal. .50, M2, HB, Flexible, a fixed developed for use on the M6 Heavy
Tank designated Browning Machine Gun, Cal. .50, M2, HB, Fixed, and a "turret type" whereby "Flexible" M2s were
modified slightly for use in tank turrets. The subvariant designation Browning Machine Gun, Cal. .50, M2, HB, Turret
was only used for manufacturing, supply, and administration identification and separation from flexible M2s.
A number of additional subvariants were developed after the end of
the Second World War. The Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, M48 Turret Type was developed for the
commander's cupola on the M48 Patton tank, and then later used in the commander's position on the M1 Abrams
tanks. Three subvariants were also developed for used by the US Navy on a variety of ships and watercraft. These included
the Caliber .50 Machine Gun, Browning, M2, Heavy Barrel, Soft Mount (Navy) and the Caliber .50 Machine Gun, Browning,
M2, Heavy Barrel, Fixed Type (Navy). The fixed types fire from a solenoid trigger and come in left or right hand
feed variants for use on the Mk 56 Mod 0 dual mount and other mounts.
AN/M2, M3, XM296/M296, and GAU-10/A
The M2 machine gun was heavily used as a remote fired fixed
weapon, primarily in aircraft, but also in other applications. For this a variant of the M2 was developed (sometimes seen
under the designation AN/M2, but it is important to note that there were .30 and .50 caliber weapons with this designation),
with the ability to fire from a solenoid trigger. For aircraft mounting some were also fitted with substantially lighter barrels,
permitted by the cooling effect of air in the slip-stream. The official designation for this weapon was Browning Machine
Gun, Aircraft, Cal. .50, M2 followed by either "Fixed" or Flexible" depending on whether the weapon was used as a fixed
forward firing gun or for use by an airplane's crew.
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Name - Browning Machine Gun, Cal. .50, M2, HB
Type
- Heavy machine gun
Origin - United States
Era - Post-WW1
Platform
- Tripod, vehicle
Target - Personnel, light-armored vehicles, aircraft
Design
date - 1918
Production date - 1933–present (M2HB)
Service
- 1921
M2HB from 1933–present
Wars
- World War II, Korean War, Vietnam
War, Cambodian Civil War, Falklands War, Desert Storm, Somali
Civil War, Iraqi Freedom, Operation Enduring Freedom, South African Border War
Specification
Weight
- 38 kg (84 lb), 58 kg (128 lb) with tripod and T&E
Length - 1650 mm (65 in)
Part
length - 1143 mm (45 in)
Cartridge - .50 BMG
Action -
Short recoil-operated
Rate - 450–600 rnds/min (M2HB) 750–850 rnds/min (M2
aircraft gun)
Velocity - 2,910 feet per second (M33 Ball) (887.1 m/s)
Max
range (updated USMC standard) - 6767 meters / 7400 yards; Max Effective Range - 1830 m (area target),
1500 m (point target) & 700 m (grazing fire)
Feed - Belt-fed
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Ron Lapp from Winnipeg,
Manitoba Canada, sent in the above three drawings along with the narrative attached, thanks Ron.
Hi Martin,
I finally received some definitive information concerning
how the expended cases and links in the solid nose 8 gun A-26B Invader were handled. I posted my question on the Yahoo A-26
forum, which you had listed on your web site, and Rick Elwood from the Pacific Coast Air Museum in Santa Rosa, CA responded
that "The 8-gun nose collected spent shells and links in a canvas bag in the lower rear part of the nose. They were removed
after each flight through a large access door in the bottom aft of the nose."
I asked him if he could send me the pages which covered
this in the technical document that he referred to (Maintenance and Erection Manual AN 01-40AJ-2) and I recently received
this excellent information.
I scanned the three pages and thought I would send them
to you and you could post them in the "Drawings/Illustrations" section of your web site if you wished. I checked with Rick
to ensure it was okay with him, and he gave me the green light. I am therefore enclosing the three pages from the Maintenance
Manual for your information.
In the e-mail that you sent me on April 14 2008, which
contained Don Vogler's comments from a B-26K armament crewmembers, it sounded like the cases and links were not collected
in a bag, but rather just piled up in the nose of the aircraft under the guns. I sent Don a subsequent e-mail to try and get
some further clarification, but as of yet, I have not heard from him. If I do, I will let you now.
The B-26, designed as a low-level attack bomber was
equipped with two remotely controlled gun turrets. The upper turret was mounted on the top of the fuselage above the bomb
bay. The lower turret, used exclusively for ground strafing, was mounted on the underside of the aircraft. In addition to
the 6 to 8 .50 calibre fixed guns in the nose, there were 6 .50 calibre guns in the wings and rocket rails. The aircraft carried
a crew of three, Pilot and Navigator up front side by side and the gunner in a compartment in the rear.
The remote control turrets were operated through a periscope
type gun sight. The Gunner occupied a bicycle type seat. A heavy duty four inch lap belt was all that held him in position.
As the Gunner sat towards the rear of the aircraft, he was subject to twice the G force of the Pilot and Navigator. Unlike
most gunnery systems that were designed as defensive weapons, the Invader systems were designed for offensive action. Special
talent was required to operate the gun switches when the aircraft was in a steep turns at high speeds and low altitudes.
The upper turret could be locked to fire forward and was
then controlled by the pilot.
Other Ordnance
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HVAR
The 5-inch FFAR suffered from insufficient speed because
of its small motor. Therefore the development of a larger rocket motor with 5-inch diameter was begun, and the first test
firings occurred in December 1943. When fitted with the warhead of the 5-inch FFAR, the rocket achieved a velocity of 1530
km/h (950 mph), making it a very powerful weapon for its time. It was officially designated as 5-Inch HVAR (High-Velocity
Aircraft Rocket), but often called Holy Moses. It became operational in July 1944, and was used by Army Air Force and Navy
aircraft.
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Napalm
The Mk 77 Mod 4 fire bomb holds approximately 75
gallons of fuel gel mixture and weighs approximately 500 pounds when filled.
The container is cigar-shaped, non-stabilized (will
tumble end over end when released from the aircraft), lightweight, and is made of aluminum. It has a 14-inch suspension between
the lugs and provides two filler holes, which are 31 degrees down from the top of the container. The filler holes are covered
by filler caps, which are secured by retainer rings. The filler caps prevent foreign objects from getting inside the container
during shipping and storage, and provides a sealed closure after the container is filled with fuel gel before fuzing. The
filler holes also provide for the installation of the primary fuses. During fuzing procedures, the filler caps are removed
and replaced by igniters, which seals the closure.
The primary fuzing system consists of the igniter
Mk 273 Mod 0 with the M918 fuze or the initiator Mk 13 (igniter Mk 273 Mod 1 with the Mk 343 fuze). The Mk 77 Mod 4 also has
provisions in the nose and tail for an alternate fuzing system using the AN-M173A1 fuze and AN-M23A1 igniter.
Functional Description
When
the fire bomb is released from the aircraft, the arming wires are pulled from the fuzes, allowing the fuzes to become armed.
When the bomb impacts the target or the ground, the container will rupture, disbursing the fuel gel mixture over the area.
The fuzes detonate, rupturing the igniters, which , in turn, ignites the gel mixture.
Fuel Gel Mixture
Fire
bomb fuel gel mixture, formerly called napalm, is a mixture of fuel and gelling solution that produces
a thickened mixture. The gel should be stringy and sticky and readily adhere to most surfaces. The fuel gelling system consists
of a fuel gelling unit, drums of gelling solution, aviation gas, mogas, JP-4, or JP-5 fuels.
The bomb bay showing 2 "Funny Bombs" and frag bomb clusters
The above photo shows what was officially named the "bomb bay spoilers"
The spoilers were installed in a slot between the bomb
bay and front wheel well. The spoilers extended completely before the bomb bay opened and retract only after the doors are
completely closed. Contrary to published statements, the spoilers were not used for strafing. They were designed to break
up the airstream entering the bomb bay. The pilots of early B-26B's without the spoilers were advised not to open the bomb
bay unless the airspeed was 240 mph or less. With the spoilers, the bomb bay doors could be opened at high speeds up to the
red-line airspeed limit.
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SSU-14/A Submunition dispenser
The SUU-14/A resembled a bundle of six pipes strapped
together, with a cap on the front end to hold them together. It ejected the submunitions out the rear. The photographic record
suggests that it was particularly popular. Configurations for the SUU-14/A included:
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CBU-14/A: BLU-3/B Pineapple bomblets, quantity unknown.
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CBU-22/A: 72 BLU-17/B white phosphorus smoke bomblets.
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CBU-25/A: 132 "BLU-24/B Orange" antipersonnel fragmentation
bomblets. The BLU-24/B did in fact look very much like an orange, sitting on a cylindrical base. It weighed 540 grams (1.2
pounds) and could throw out 300 steel fragments.
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CBU-57/A: 132 "BLU-57/A"
Some sources mention that the SUU-14/A also carried a
minelet known as "gravel" in Vietnam. It was apparently nothing but a small lump of plastic explosive that was packed in a
freon-filled container and became very shock-sensitive when it dried after dispersal. Details are very unclear, with pictures
available showing a wedge-shaped cloth packet designated "XM27", or square cloth packets with the designation "XM40", "XM41",
"XM44", or "XM65".
Cluster submunition dispensers were often used in Vietnam
by search and rescue support aircraft, such the Douglas A-1 Skyraider. Riot gas loads were useful for interfering with the
work of antiaircraft gunners, and a Skyraider could lay down a carpet of minelets behind downed aircrew on the run to block
pursuers.
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"Rockeye" Cluster
Bomb
The CBU Mark 20 Rockeye II was an antitank cluster bomb
that dispensed 247 shaped-charge bomblets. This unguided free-fall weapon was developed by the U.S. Naval Weapons Center in
1963 and was produced in 1967. Weighing close to 500 pounds, the CBU Mark 20 was delivered by aircraft to the target area
and upon release opened to expel anti-tank bomblets that could destroy a number of targets on the ground simultaneously.
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