M40 Recoilless Rifle
The M40 Recoilless Rifle was the largest and most powerful recoilless rifle in the US Army's arsenal when it was introduced in 1955. It was a refinement of the Korean War-era M27 105mm recoilless rifle, which had been hurriedly produced and proved to be unreliable, too heavy, and to lack any means of accurately placing fire at long range. With the adoption of the M40, the M27 was immediately withdrawn from service, with most examples being given away to US allied states but a few ending up transferred to, of all places, the United States Forest Service and United States National Park Service, who used them alongside the 75mm M20 Recoilless Rifle for starting controlled avalanches until the US Army's reserve ammunition stockpiles were exhausted in 1999.
While the M40's ammunition is referred to as 106x607mmR, the actual bore of the weapon is 105mm (4.1 inch): the different designation was to prevent accidental issuing of M27 ammunition, which the M40 could not fire. Ammunition for the M40 included anti-tank shaped charge HEAT, HEP / HESH (high explosive plastic / high explosive squash head) and APERS canister rounds (containing 6,000 13-grain nail-like steel flechettes and commonly called "beehive" rounds), and Spain manufactured an additional HEAP (high explosive anti personnel) round.
The M40 incorporated an optical sight on an "arm" sticking out from the left side of the gun tube as standard and could also mount an AN/TVS-2 7x night vision spotting scope for night operations. To remedy the accuracy issues of the M27, the designers at the US Army's Benét Laboratories looked to Remington, who developed the M8C Spotting Rifle. This is a gas-operated semi-automatic .50 caliber rifle feeding from a left-side-loading 10 or 20 round magazine and ejecting to the right. The M8C is mounted on the top of the M40's gun tube. Both weapons share a common trigger, a mushroom-shaped button in the middle of the elevation handwheel on the left side of the weapon: pulling this outwards fires the spotting rifle, while pushing it inwards fires the M40. The British were impressed by the M8C and manufactured it under license as the L40A1 for their WOMBAT 120mm recoilless rifle, replacing the Bren gun used for ranging on the earlier MOBAT. It is from the BAT series that the 12.7x77mm spotting round got its unofficial designation.
The ground version of the M40 was mounted on the M79 "wheelbarrow" tripod for infantry use (with the exception of the M40A4 variant, which used a conventional 3-leg M27 tripod) with a single front wheel and two solid legs which could be picked up by the 4-5 man crew to quickly relocate it. The weapon is aimed by the gunner sitting on the tripod leg with the wheel and operating a pair of handwheels, a traverse wheel located on top of the pivot and an elevation handwheel on the left side, though the traverse wheel can be declutched to allow for quick movements. Elevation of the M79 mounting was -17 to +65 degrees with a full 360 degrees of traverse.
The bizarre M50 Ontos light tank carried six of a variant only used by it, the M40A1C, on two "arms" on its turret holding three rifles each, with four spotting rifles mounted on the guns at the top of this array. It was commonly mounted on APCs, and due to the recoilless operation could be carried by light vehicles such as Jeeps to give them far greater hitting power than would be possible with a conventional gun, even being able to be fired off the tiny M274 Mechanical Mule despite weighing about half as much as the vehicle itself. The M40 is still commonly mounted on technical trucks in conflict zones.
The M40 was used extensively during the Vietnam War, but was largely replaced in US service by the BGM-71 TOW in the role of heavy infantry anti-tank weapon during the 1970s. It was exported and produced under license by many US allies: most are identical to the US version, though the Austrian variant uses a two-wheel carriage designed to allow it to be towed by vehicles. China copied the M40 as the Type 75, a variant that uses an electronic laser rangefinder instead of a spotting rifle, and which is usually carried on a modified 4x4, and Iran produces a local copy with a name that translates as "Anti-Tank Gun 106." The M40A2 and M40A4 variants still hanging around in US stockpiles are why the M40 Sniper Rifle jumped from A1 to A3 to A5.
As a point of interest, the M8C spotting rifle is the source of the long-standing myth that it is in some way illegal to fire .50 caliber rounds at infantry. This was actually because US doctrine for this weapon strongly discouraged using the spotting rifle as an anti-infantry weapon since it would give away the M40's position. The impact-detonated incendiary filler in the M48 spotting round (designed to produce a small puff of smoke on impact) may also have led to concerns that this specific round would not be legal.
The M40 Recoilless Rifle and variants can be seen in the following films, television series, video games, and anime used by the following actors:
(1955 – 1970s, still in US inventory and produced by third parties)
- Type: Recoilless Rifle
- Origin: United States, primary manufacturer Watervliet Arsenal of New York
- Caliber: 106x607mmR (actual bore size 105mm) & .50 BAT (12.7x77 mm)
- Weight: 462 lbs (209.6 kg) (complete weapon including M8C on M79 tripod, empty) + 15 lbs (6.8 kg) if mounting A/N-TVS-2 night vision scope, 24.4 lbs (11.1 kg) (M8C alone, empty)
- Length: 11 ft 2in (3.4m) (M40), 45 in (114.3 cm) (M8C)
- Barrel length: 8ft 10in (2.7m) (M40), 32 in (81.3 cm) (M8C)
- Feed System: Breech-loaded single shot (M40), 10 or 20 round detachable box magazine (M8C)
- Fire Modes: Single shot (M40), Semi-auto (M8C)
|Godzilla vs. Gigan||JGSDF personnel||Mounted on jeeps||1972|
|We Want the Colonels (Vogliamo i colonnelli)||Italian troops||Mounted on jeeps, in documentary footage||1973|
|Raid on Entebbe||Israeli commandos||Mounted on jeeps||1977|
|Lone Wolf McQuade||On Austrian 2-wheel carriage||1983|
|The Return of Godzilla||JGSDF personnel||Mounted on Type 73 Light Trucks||1984|
|Red Scorpion||Dolph Lundgren||Rachenko||Mounted on Soviet base||1989|
|April Captains (Capitães de Abril)||Portuguese soldiers||Mounted on jeeps||2000|
|Going Back||Jaimz Woolvett||Tex Atkins||2001|
|Going Back||Kenny Johnson||'Jimmy Joe' Coulter||2001|
|Kong: Skull Island||US soldiers||Stock footage of an M40 mounted on an M274 Mechanical Mule in Vietnam||2017|
|Game Title||Appears as||Note||Release Date|
|Battlefield Vietnam||Mounted on M50 Ontos||2004|