By: Warren Gray
Copyright © 2022
“The (30mm) recoil was just a touch too much.”
— Chris Fellegy, CFDI Helicopter Systems, 2022.
The introduction of the AH-64A Apache attack helicopter into U.S. Army service in 1984 heralded the age of a very-powerful, new, 30x113mm cannon, the M230 Chain Gun. This gun is a single-barrel, chain-driven autocannon, capable of firing 300 to 625 rounds per minute (five to 10.4 rounds per second), produced since 2019 by Northrop Grumman Innovation Systems. This weapon was originally designed for an air-to-air, anti-helicopter role, utilizing the same ammunition as the French DEFA 553 revolver cannon employed in jet fighter aircraft, but has since been adapted for multirole use, with M789 High-Explosive, Dual-Purpose (HEDP), lightweight-alloy ammunition.
Each M789 round contains three-quarters of an ounce of sealed, shaped-charge explosive, with a liner that collapses into an armor-piercing jet of metal, capable of penetrating one inch of rolled, homogeneous armor at 550 yards. The outer shell is designed to fragment upon impact, with a lethal radius of about five feet.
This innovative Chain Gun is aimed by an electronic, helmet-mounted sight on the gunner’s head, from the front seat. The weapon itself is rotated, raised, or lowered by hydraulic actuators, which also act as a recoil-attenuation system to reduce the harsh, 1,750 pounds of recoil momentum produced by the mighty cannon.
There are essentially seven different methods to mitigate recoil force in any weapon: 1. Adding weight, which is usually an undesirable trait for an aircraft gun. 2. Hydraulic buffers, which act as shock absorbers. 3. An efficient, muzzle-brake design, to deflect muzzle blast slightly backward. 4. A rubberized, soft mount or cradle to absorb some of the shock. 5. Strong, recoil springs to soften the rearward force. 6. An internal buffer, usual manufactured from polyurethane. 7. Or a soft, rubberized, recoil pad, such as those frequently used on shoulder-fired weapons, like rifles and shotguns.
The M230 is a 130-pound cannon, with an effective firing range of 1,640 yards (.93-mile), and a linkless-feed system. There is also an M230E1 version, with linked or linkless feed mechanisms, capable of firing both 30x113mm DEFA ammunition and 30x111mmm British ADEN ammunition The latter can be mounted on the Apache gunship.
In addition to the AH-64 aircraft, the M230E1 Chain Gun also is carried by the 16 MH-60M (or AH-60M) Black Hawk Direction-Action Penetrator (DAP) gunships of the elite 160th Special Operations Aviation Regiment (Airborne), or 160th SOAR(A). The gun is usually mounted in a fixed, forward-firing position beneath the left wing, but with no special, recoil-reducing measures. In fact, in 2017, the U.S. Special Operations Command issued a $666,229 contract to Orbital ATK to modify the weapon to reduce vibration and the substantial muzzle blast.
In September 1980, a prototype, M230 cannon was fitted on an experimental basis to the belly of a small, camouflaged, Hughes 500MD Defender scout helicopter (#N8337F) at the Farnborough Airshow in England. This was several months before the creation of the 160th SOAR(A), which immediately adopted AH-6 (MD500D) helicopter gunships. However, during actual testing, the recoil from the cannon proved to be excessive, cracking the airframe, so the gun was never incorporated onto these smaller, attack aircraft.
During the mid-1990s, Contract Fabrication and Design, International (CFDI) of Princeton and Denton, Texas, created an all-new, LR-30 (Low Recoil, 30mm) cannon of their own design. It was similar in size and general configuration to the M230, but was stated to be, “With the lowest recoil force of any 30mm cannon anywhere,” just 600 to 800 pounds of recoil force, firing, standard, NATO 30x113mm ammunition. This weapon fires at a rate of 250 rounds per minute (about four rounds per second), with either a six-round clip, a 30-round, linkless feed system, or a standard, belt-feed mechanism. Recoil is reduced with a combination of an effective muzzle brake, strong springs, and a soft, cradle mount.
The LR-30 gun was constructed to be versatile enough to serve as a fixed, forward-firing weapon; a hand-fired, helicopter door gun; a vehicle-mounted weapon; or a manually-fired, ground weapon on a tripod. An interesting variant of this powerful cannon is the AH-6/MD500 system, which adds a 38-inch-long, six-inch-wide, blast tube over the length of the barrel (visually resembling a very short, 105mm howitzer) attached to the left side of the aircraft. The purpose of the tube is to reduce blast pressure and deflect it away from the aircrew, with special slots near the rear to keep the muzzle brake effective.
According to a recent email from Chris Fellegy, the Technical Sales Manager for CFDI, “It was tested on our personal MD500, and…the 160th MELB (AH-6MMission-Enhanced Little Bird) and (M)H-60 DAP aircraft as well…live-fire testing on the MELB Little Bird was successful, but the recoil was just a touch too much…Just prior to qualification, it seems a lack of funding prevented the program from crossing the finish line. So close, only two units were built.”
The requirement for such powerful, helicopter-borne cannon, especially in the ground-attack role, has been negated largely by the advent of newer, smaller, laser-guided missiles replacing the unguided, 70mm or 68mm rockets of the past. These new, super-accurate weapons still use Hydra-70 rocket bodies and 10-pound warheads, but the nose and tail kits have been replaced with a laser seeker and movable, control fins. The most-notable examples include the AGR-20B APKWS II (Advanced, Precision-Kill Weapon System II), Lockheed Martin DAGR, Raytheon Talon, and Thales FZ275 missiles. Because they are all fired from existing rocket pods, with the exhaust plume blasted out the back, there is virtually no recoil with these weapons.
Now, we’ll examine some ground-based applications for a low-recoil, 30mm cannon. In 1980, the Soviet BMP-2 armored personnel carrier (APC) introduced an extra-powerful, 30x165mm 2A42 main cannon for attacking armored vehicles. Because the BMP-2 was such a heavy vehicle itself, the very stout recoil was not a problem. The United States and NATO developed their own, smaller-caliber, anti-armor weapons at approximately that same time, beginning in 1981 with the M242 Bushmaster cannon in 25x137mm, the Mk 44/XM813 Bushmaster II chain gun in 30x173mm, the Bushmaster III in 35x228mm, and the Bushmaster IV in 40x365mm. These are all great weapons for heavy, armored vehicles, but a lighter-recoiling cannon is desired for smaller, high-mobility, patrol vehicles.
This requirement led to the M230LF (LF for Link-Fed) design for ground-based or naval applications. It is basically an M230E1Chain Gun, modified with a longer barrel (60 inches, versus the original 45 inches); the length adds weight (30 extra pounds overall) and reduces recoil slightly. It also has a linked feed system and a slower rate of fire, at just 200 rounds per minute or 3.3 rounds per second, which also reduces the recoil somewhat.
Kris Osborn of KTVZ News in Arizona had the opportunity to manually fire an M230LF in early September 2021, in Kingman, Arizona. He wrote that, “It looked like fire lighting up the air, accompanied by a very loud noise, smoke, and the sight of a large, fiery explosion on the other side of a desert canyon. The backward thrust was very powerful, throwing me back what felt like several feet. All this seemed to happen at once, when I first tried to fire an M230LF Lightweight 30mm Cannon Chain Gun, an extremely-lethal, rapid-fire gun now arming the Army’s armored Stryker vehicle (the IM-SHORAD Air Defense System)…I was shocked by what seemed to be its destructive power. It did not just ‘hit’ or ‘go through’ a target, it exploded it, yet with precision targeting, placing multiple, fast-moving, Chain Gun rounds through the same target hole, one after the other.
“The M230LF has better target effects against light-skinned, armored vehicles… and frankly, it can be hard to miss short-range targets, it seems, with an automatic gun with these kinds of targeting and firing technologies…I was required to wear earplugs and body armor. My instructor told me to press my chest against the mount so as not to be literally thrown back by the force of the cannon. The force of the shot is intense, particularly when it rapid-fires multiple rounds in succession like a machine gun. The 30mm rounds, shooting out of the gun with rapid fire, look like small balls of fire flying after one another out of the end of the cannon.”
The very latest version of the M230 Chain Gun is the XM914E1, which is nearly identical to the M230LF in most aspects. However, it uses a percussion-primed, firing pin instead of electrical ignition of cartridges, weighs 170 pounds, and uses the all-new, XM949 HEDP (equivalent to M789) round to engage ground targets, and the XM1198 (HEDP-SD) self-destructing round to engage aerial targets.
Northrop Grumman is currently offering their Sky Viper 20mm Chain Gun, as of March 2021. It is a scaled-down version of the combat-proven, M230 weapon, for the Future Attack Reconnaissance Aircraft (FARA) requirement for either the Bell Invictus 360 or the Sikorsky Raider X armed helicopter. Every effort has been made to reduce the overall weight of the weapon, which is just 81 pounds (less than a .50-caliber, Browning M2 machine gun), and lower the recoil forces, while increasing the rate of fire past 625 rpm (probably 750 rpm, like the single-barrel, Nexter M621 20mm cannon.)
The Sky Viper is geared toward a high degree of accuracy, with fewer rounds fired, and more rounds impacting the target. A new family of specialized, ultra-lightweight, XM1031/1032 aluminum-cased ammunition will further reduce overall system weight. This weapon would make an excellent, lightweight replacement for the 134-pound, .50-caliber, GAU-19/B Gatling gun mounted the 160th SOAR(A)’s AH-6M Little Bird gunships. It would also be a great, viable replacement for the M3M machine guns in the wings of A-29A/B Super Tucano counterinsurgency aircraft flown by USSOCOM, and the air forces of Brazil, Chile, Colombia, Ecuador, Lebanon, and several more nations.
The Sky Viper will be competing against the company’s own XM915 three-barrel, 20mm Gatling-gun design, which weighs 115 pounds and fires up to 1,500 rpm. It’s the lightest, 20mm rotary cannon in the world, firing at twice the rate of a single-barrel weapon. This gun is also a possible replacement for the earlier, M197 20mm Gatling gun, weighing in at 132 pounds. But the fast-firing XM915 generates a hefty recoil force of 2,500 pounds, so it’s hardly a low-recoil weapon.
The very latest evolution of 30x113mm cannon is the AEI Systems (of Ascot, England) Venom LR (Low-Recoil), designed in 2019, and now entering production. This is a traditional, gas-operated, electrically primed, revolver cannon. It is a complete redesign of the venerable, well-proven, ADEN (Armament Development, ENfield) aircraft gun from 1953, intended for light reconnaissance vehicles, remote weapon stations (RWS), and naval fast-patrol vessels.
It fires at either 225 rounds per minute (3.75 rounds per second) or a breathtaking 1,200+ rounds per minute (20+ rounds per second), with an integrated buffer cradle, twin, barrel-aligned, recoil buffers, and an efficient muzzle brake that combine to improve accuracy and to reduce its recoil force by almost 70 percent (from 5,246 pounds down to 1,574 pounds) compared to the standard, ADEN gun, from which it was derived. It’s also reported to be nearly 50-percent less expensive than the Chain Gun. The barrel is 55 inches long, which is eight-percent shorter than the M230LF barrel.
In addition, AEI is working on a more-powerful version of the Venom cannon in 30x173mm, as used in the GAU-8/A Avenger Gatling gun on the A-10C Warthog attack aircraft, the side-firing, GAU-23/A weapon aboard AC-130J Ghostrider aerial gunships, and the Bushmaster II main gun on the Army’s M1296 Stryker Dragoon armored vehicles.
In any event, there continues to be a global demand for low-recoil, 30mm cannons that are powerful enough to destroy armored vehicles, with growing emphasis on accuracy and long range, even at the expense of a reduced rate of fire. The M230LF Chain Gun still leads the pack in overall demand and versatility for weapons in this category, but it is constantly evolving and improving to meet the rigors of modern warfare.
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Warren Gray is a retired, U.S. Air Force intelligence officer with experience in joint special operations and counterterrorism. He served in Europe and the Middle East, earned Air Force and Navy parachutist wings, and four college degrees, including a Master of Aeronautical Science degree, and was a distinguished graduate of the Air Force Intelligence Operations Specialist Course, and the USAF Combat Targeting School. He is currently a published author and historian. You may visit his web site at: warrengray54.vistaprintdigital.com.