Since U.S. Ordnance received the NSN and contract, they must perform “first article” inspection and testing. There are more than 186 parts inspections that must be accomplished. Each one must meet the military standards for production. There is also a testing protocol called for in MIL-G-70790 (AR), the Military Specification for Gun, Machine, 40mm MK19 Mod 3, which must be strictly adhered to and passed with government inspectors viewing. In the previous article, we reviewed the relevant first parts of the testing we observed. Now it’s time to go live, but there are more checks to perform before we can start.

MK19 Mod 3 Specifications

In section 3.3 of the Mil-Spec, gun sights and bore calibration are checked. The wedge optic mount on the right side in the MWO has to be perfect for calibration, which we did check. Then, in 3.4 and 3.5, it’s an ammunition compatibility check to ensure all the various 40x53mm rounds will chamber and fire. Done. Then, as stated in 3.5.1, “Proof Testing: The machine gun shall withstand the firing of one M385A1 40mm cartridge without any evidence of part failure, deformation, or loosening.” Done.

The M385A1 round has a one-piece solid aluminum projectile with a rotating band in an M169 cartridge case. The propellant is M2 (4.2g, 0.15 oz.). The primer is an FED 215 percussion-type. The ogive of the M385 series matches the shape of the M430/A1 HEDP projectile, which has 45g (1.61 oz.) of Comp A5 explosive, a shaped charge with copper liner, and a pre-fragmented body. It’s just the ogive that matches. The M385 series frequently is indented at center, which is weight lightening to match the weight of the M430 round. The M385A1 uses M16A2 links only (The M385 can use either M16A1 or A2).

There are protocols, as mentioned. Firing must be done in a proper, specified cadence to allow proper cooling periods, simulating the long life of a MK19 Mod 3 in service. Cleaning intervals must be followed, as well as inspections, including some testing that might appear redundant, but is necessary to achieve the full results of the test.

Benchmarks in the MK19 Mod 3 MIL-Spec First Article Acceptance Test

(SADJ covered many of these items in the first article in this series, it is online at www.sadefensejournal.com, if you would like to refer to it).

Spoiler Alert: U.S. Ordnance’s MK19 Mod 3 program has passed all of the MIL-Spec testing and is in the third phase. They are the only source of U.S.-made MK19 Mod 3 machine guns accepted by the U.S. military.

• Pre-Firing Inspection There are 19 points to cover in this visual inspection.
• Ammunition Compatibility Check This is done with a variety of issue rounds supplied by the customer. There are 12 steps in this process, covered in our first article.
• Gun Sight and Bore Calibration Check There are 12 steps in this process, covered in this article.
• Proof Inspection This is a 3-part inspection involving firing on round of M385A1 ammunition.
• Firing Mode This is a test in 8 parts of the firing mechanism including the solenoid remote firing.
• Belt Pull A four-part test, done with free hanging 28-round belts, in two to four round bursts. We performed this test in the first article, but again throughout the second testing.
• Cycling Rate of Fire Measured with 10-round belts. Interestingly, the string of rounds is not averaged for rate of fire but measured individually to meet the required rate.
• Trunion Load Performed in the test report in this article.
• Accuracy At 1000m, a 14m target is set. Firing is done in 2-3 round bursts and all rounds must hit the target. Performed both test days we were there for.
• Post-Firing Cleaning At all times that are called for, a full inspection is done for proper cleaning and reassembly. Parts are inspected according to 9 focus points.
• Interchangeability In the first article we did, we covered some of this, but the further full testing has more of this, and a special station is set up.
• Reliability The longest part of the test, It begins with firing 192 rounds, and repeating it after rounds 152, 2304, 3456, 4608, and 5760. It is a specific cadence, intended to show any dispersion changes, or other issues.
• Full Cleaning and Inspection Specified at every 2,304 rounds. The guns are completely disassembled, visually and magnetic particle inspected, cleaned, and properly lubricated. Parts to lubricate are the bolt, barrel, firing pin cover, firing pin, bolt sear, firing pin sear, receiver, lock plate, and feed tray.

In Section 4.5.8 “Trunnion Load”

• A. For First Article Inspection, this test shall be performed concurrently with the belt pull test.
• B. Mount a Quartz Force Link Cell Kistler Model 9362 with a Charge Amplifier Model 504E and a Filter Model 545A (Or Equivalent) directly below the receiver, below the locking pin, integral with the mount and in alignment with the receiver buffers.
• C. Record a time-load trace of recoil using a Honeywell Visicorder Modl 1858 with a TCD (tape compatible differential) Amplifier Model 1887, or approved alternate equipment.
• D. Trunion load forces are to be measured at the mounting point. The last three (3) rounds of the belt fired shall be discounted.

The mount shown here is a special mount custom made to the government specification for the test. The Kistler Force meter is a very expensive and sensitive piece of equipment, yet it is built to handle the recoil forces of larger forces than will be in this test. The reason for testing during the belt-pull test are based on finding variations in the side weight of the belt, and as the belt lightens the forces will change. This data will be valuable to see the consistency of the construction. After this first article test, the trunnion load tests will be less frequent but based purely on the single rounds fired. 

After test-cycling the MK19 with dummy rounds, this is what they look like. Note that the links are de-linked and pushed to the rear. In the closeup, the male and female end of the links are evident.

The male end must be pulled out of the female, to the rear. Thus, when a can of ammunition is first opened, the first round will present with a female end of the link to feed into the feed tray. On cocking, the round is pulled to the rear, then slammed forward into the barrel, pushing the single link rearward on the body of the casing, and ejecting it. When fed into the HK GMG machine gun, because it pushes through forward, the belt must be presented opposite, with the male link into the feed first. This requires taking the belts out of the can before using and reversing the belt.

In U.S. Ordnance’s instructor classroom, they’ve made a custom factory cutaway of the MK19 Mod 3 as a training aid. We are curious if these will be available for contract sales.

The Rifle Grenade Launcher

During the late 1950s, the M7A3 grenade launcher adapter was being issued for use on the M1 rifle. After the M14 rifle replaced the M1, the M76 grenade launcher was adopted. For accuracy, the M15 tilting-bar sight, designed to be attached to the M14 rifle’s stock, was issued for use with the M76 launcher. Special “grenade launching cartridges” were used. Rifle grenades could also be launched from the M16 rifle, but no special adapter was needed; grenades could be slipped over the NATO standard 22mm diameter flash suppressor. Disadvantages of launching grenades from rifle barrels included: short range, inaccuracy and heavy recoil that would sometimes break buttstocks.

Clearly, a new weapon was needed, one that could provide accurate direct and indirect fire to fill the gap between the rifle, hand grenades and the light mortar. During the 1950s the United States Ordnance Department began development of a weapon that could fire high explosive munitions, multiple projectile anti-personnel rounds and smoke and illumination rounds.

40mm Ammunition

During the early 1950s the Ballistic Research Laboratories at the Aberdeen Proving Ground developed a 40mm high-explosive, fragmentation projectile. The goal was a range of 400 meters at the relatively low velocity of 250 feet per second, with a recoil force no more than that of a 12-gauge shotgun. The new projectile used a high-low pressure system, which was developed by the German firm of Rheinmetall-Borsig during World War II for their 8cm 8H63 anti-tank gun. The advantage of the high-low system was that a lightweight barrel could be used, reducing the overall weight of the weapon.

The M79 Grenade Launcher

The concept of a lightweight weapon capable of projecting a grenade further than could be thrown by hand and could exceed the range of rifle-launched grenades was coordinated by the Small Arms Development Branch, headed by Colonel Studler. Jack Bird, a deputy to Colonel Studler, took an interest in the project; he built a crude launcher and brought it to the Pentagon to demonstrate. The device was comprised of a short length of tubing with the same inside diameter as a golf ball. To operate the “launcher,” a golf ball would be placed inside the tube and compressed against a spring. The golf ball was secured in place with a nail. Upon removing the nail, the golf ball would be launched. Bird, an avid golfer, suggested the name “Project Niblick” after the number nine iron, a high lofting golf club.

During 1953, the Project Niblick grenade launcher was under development at the Springfield Armory under the guidance of Cy Moore, with Dave Katz, a design engineer. The Picatinny Arsenal provided 40mm practice grenades for firing in the prototype launchers. There were three types of launchers being developed: a crude shoulder fired test fixture, a pistol and a three-shot semiautomatic launcher. The fixture was primarily a means of testing the ammunition to get an idea of the range and accuracy. The weight of the projectile was approximately 5.3 ounces. When launched with a quadrant elevation of 35 degrees, it had a range of 400 meters. Development commenced at the Springfield Armory. Proposed designs were identified by a letter “S” representing the Springfield Armory. Many of the designs never made it any further than the drawing board.

The Infantry Board at Fort Benning stated that they preferred a three-shot grenade launcher. A barrel length of 14 inches evolved as the length to make it unlikely that the gunner could get his fingers in front of the muzzle while firing. The three-shot launcher achieved semiautomatic operation through the use of a clip made up of three side-by-side chambers, each long enough to house a cartridge about 3.5 inches long. The clips would move to the left after firing by a constant force of a negator spring. As each round was fired, a latch detected the launching of the projectile and allowed the clip to move over until stopped by the next projectile, lining up that cartridge with the barrel. Although the basic concept was simple, the mechanism proved to be complex and unreliable. Continued misalignment between the projectile on the bore created gas leakage and a loss of accuracy. Special purpose rounds, such as CS gas or signal flares with a longer overall length, could not be used. The simplest design, designated as the “S-5,” was a single-shot, break-open type weapon. The S-5 evolved into the XM79 in 1959 after the three-shot S-6, T148E1 project was canceled.

After the idea of a multi-shot, semiautomatic launcher was scrapped, it was replaced by a simple, single-shot weapon, patterned after a break-open type shotgun. One launcher was ordered from Dave Mathewson, who operated a local fabrication shop, often used by the Springfield Armory. To keep the weight at a minimum, the weapon featured a hard-coated aluminum barrel. The odd shape of the stock was designed so that the bottom edge would be aligned with the line of recoil; the top or comb is contoured to keep the grenadier’s head upright owing to the line-of-sight relief when firing at low angles. To reduce the effects of the recoil on the shooter, a rubber recoil pad was fitted to the butt of the stock. The Infantry Board suggested a folding leaf sight mounted on the barrel with a bead front sight just above the muzzle. The XM79 launcher was sent to the Infantry Board in 1956 and was recommended for type classification in 1957.

To load the weapon, the operator simply moves the barrel-locking latch counter-clockwise to open the breech. Moving the release latch automatically puts the weapon into a safe position; opening the breech cocks the weapon. After closing the barrel, the safety must be pushed forward to fire. The weapon is easily field stripped by removing the front sling swivel screw and removing the forend. The barrel can then be disengaged from the fulcrum pin and separated from the receiver group.

The weight of the loaded launcher is 6.45 pounds; overall length is 28.78 inches. The stock and forearm are made of walnut. The rest of the weapon, except for the aluminum barrel, uses steel parts phosphated for corrosion protection. The original contract price for the M79 was $318.00 each. The M79 was issued with a small arms accessory case, which included a bore brush, plastic oil tube, combination tool and cleaning brush. Early carrying cases for the kit were made of canvas, later changed to vinyl.

During testing by the Infantry Board in June 1960, it was recommended that a new rear sight for the M79 launcher be designed and fabricated. The new sight was completed in October 1960. The early ladder-type sight was replaced with an adjustable, single crosspiece-type sight with a correction for azimuth. All launchers produced up to June 1960 had to be retrofitted. Confirmatory tests in December 1960 revealed requirements for additional windage adjustment on the rear sight. The additional sight modification was incorporated in the first production run. R&D continued in order to improve the reliability and function of the weapon. The launcher was considered acceptable by the Continental Army Command (CONARC) and was subsequently type-classified as the Launcher, Grenade, 40mm, M79 on December 15, 1960. By the first quarter of 1961, the new adjustable rear leaf sight was in full production, and several mandatory changes were implemented on the barrel locking lug, trigger spring and front sight.

The heat and humidity being experienced in Vietnam were causing problems with the warping and swelling of the wooden stocks of the M79. As a result, work began on designing a plastic buttstock and foregrip for the weapon. By 1964, a suitable plastic buttstock was available; General Tire was the primary contractor. There were no plastic foregrips adopted.

Although the M79 grenade launcher was designed and developed at the Springfield Armory, the majority were manufactured by civilian companies. Contracts awarded to private industry included: Action Manufacturing Company, Philadelphia, Pennsylvania, Contract DA-11-1199-ORD-736 and Exotic Metal Products, Pasadena, California, Contract DA-11-199-ORD-730. Other contracts were subsequently awarded to the Kanarr Corporation of Kingston, Pennsylvania, and Thompson Ramo Woolridge (TRW) of Lyndhurst, Ohio. The decision to have private companies manufacture the M79, resulted in a lot of resentment with the civilian employees of the Springfield Armory. Series production ran from 1961 to 1971 with an estimated 350,000 M79 launchers produced.

Despite being replaced by modern grenade launchers, like the M320A1 and the M32A1, the M79 is still being fielded by the U.S. military.

The China Lake Grenade Launcher

Developed for the U.S. Navy SEAL teams was a limited production, pump-action 40mm grenade launcher, fed from an under-barrel tubular three-round magazine. The launcher was fitted with M79 front and rear sights and a shotgun-style stock. There was no official designation other than “The China Lake Grenade Launcher.” The weapon was developed at the Naval Weapons Center, China Lake, California, during 1967-1968.

The XM148 Grenade Launcher

While the adoption of the M79 grenade launcher solved one problem, it created another; it reduced the number of riflemen in a squad, the man carrying the single-shot M79 was usually armed with only a pistol for self-defense. To address the problem, the concept of the rifle-mounted launcher was studied. The 40mm XM148 launcher, first issued in 1967, was designed for mounting under the barrel of an M16 rifle. The weapon was developed by Colt Firearms to allow each rifleman in an infantry squad the ability to launch 40mm grenades, rather than one man equipped with an M79. During field testing in Vietnam, a number of problems were encountered. The XM148 launcher was not considered reliable or safe enough for type classification, and the launchers were pulled from service; most were destroyed.

The M203 Grenade Launcher

After the XM148 grenade launcher was scrapped, the concept of a rifle-mounted launcher was not. The Army initiated a competitive program for a new 40mm rifle-mounted grenade launcher. Designs were submitted by Aircraft Armaments Inc., Ford Aerospace and Communications Corporation and Aerojet Ordnance and Manufacturing Company. During August 1968, the Aircraft Armaments (AAI) design was type-classified as the XM203 grenade launcher. A small lot was manufactured and shipped to Vietnam for field testing. AAI’s XM203 40mm grenade launcher was found to be simple, safe and reliable. After successful testing and evaluation, the Aircraft Armaments design was type-classified as the Launcher, Grenade 40mm, M203 in 1969. Ironically, Aircraft Armaments, who developed the weapon, did not have the capacity to produce the number required by the Army, and a contract to manufacture the M203 was awarded to Colt Firearms. The U.S. M4 Carbine version of the M16 was adopted in 1994. The M203 launcher would not fit on the shorter M4. The M203 GL was modified into the M203A1, which is functionally the same as the M203 but is designed to fit on the M4 and M4A1 carbines. The quick-release M203A2 was designed for M4 carbines with a rail system and with M16A4 rifles that have the M5 adapter rail. Currently, there are at least seven U.S. companies manufacturing the M203 grenade launchers and its variants.

Recent images from the Russian seizure of the Crimean peninsula have highlighted the range of weaponry employed by Russian forces and combatants identified as either pro-Russian militias or private security contractors. Amongst these weapons is the GM-94, a pump-action grenade launcher chambered for a proprietary 43mm cartridge. These polymer-cased rounds are available in HE, HE-FRAG, thermobaric, illumination, smoke, and various less-lethal loadings. The GM-94 is fed from a three-round tubular magazine (3+1 capacity) located above the barrel, and the weapon features a double-action trigger and manual safety.

The presence of these weapons would be consistent with claims of Russian Special Forces (Spetsnaz) or Russian-backed private security contractors operating in the region. Regardless, it is important to note that the GM-94 has been observed in several other countries, including Ukraine, Kazakhstan, and even Libya.

GM-94 grenade launcher. (Alexander Garr)

Numerous other weapon systems have also been observed in the hands of pro-Russian forces in civilian clothes or unmarked uniforms, including AK-74M, AKS-74N, AKMS, and AS “Val” rifles, SVD, SVDS, and VSS sniper rifles, PKM and PKP machine guns, GP-25 and GP-30 under-barrel grenade launchers, and PP-9 “Klin” submachine guns. Many of these weapons have been fitted with post-production accessories, including rails, foregrips, PBS series suppressors, and various optics.

(This article is reproduced courtesy of Armament Research Services (ARES) – www.armamentresearch.com and was originally published on March 2, 2014.)