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.

Art Pizza dedicated more than 38 years serving the U.S. Army in its Armament Research, Development and Engineering Center (ARDEC) (which is now known as the Combat Capabilities Development Command, Armaments Center) at Picatinny Arsenal. In that time, he spent 17 years as a project engineer on the Mk19 grenade machine gun. He spent five years on the Green Ammo project (5.56mm and 9mm). Then he became the center’s Technical Expert on 40mm ammunition. He later went back into design and became the ARDEC Project Officer on hybrid ammunition (including mortars) and the extended range guided 40mm projectile. Pizza spent the last five years before his retirement as the Project Integrator for Medium and Small Caliber Weapons, Ammunition, and Fire Control systems.

We sat down with Pizza to discuss his long and distinguished career.

Small Arms Defense Journal: Art, thank you for your service to the U.S. Army and the 40mm weapon platforms. We greatly appreciate you taking the time to connect with Small Arms Defense Journal. You have the unique perspective of spending significant time in both 40mm weapons and 40mm ammunition. To solve the age-old question – when there is a system failure, who’s usually to blame, the ammo guy or the weapon guy?

Art Pizza: Around the late-1970s or early ‘80s, when the U.S. Army transitioned the Mark19 40x53mm weapon from the Navy, they were hand fitting/gunsmithing each weapon making 3-7 guns a month at Navy Ordnance Station in Louisville, Kentucky. They were beautiful, hand-built weapons; however, the production numbers were nowhere near the rate the Army needed. The Army was looking to make over 250 weapons a month. They end up contracting to Saco Defense (now General Dynamics Saco, ME). The complete Technical Data Package needed to be reworked. They worked closely with Saco Defense in manufacturing the weapon and improving the mass production and tolerances to make it at a high production rate weapon.

At the same time, we needed to increase the production rate of 40mm High-Velocity ammunition. The Mark19 is an advanced primer, blowback-operated weapon in which the bolt never locks into the receiver and depends on the firing pin tripping as the heavy bolt is moving forward. The velocity of the bolt moving forward is critical to the functioning of the weapon. The contracted 40mm ammunition at that time was purchased as individual components and sent to Milan AAP for final load, assembly and packing into cartridges. Most of the issues pertained to the consistent crimping of the cartridge case (a new 360-degree roll crimp vs. the old, staggered stake crimp.) Unfortunately, the failure to obturate because of the crimp issues caused stuck projectiles in the Mark19. If a second round was fired into the first projectile, on rare occasions it could cause a low-order explosion. This was called an in-bore detonation.

Other ammunition issues early on were related to improper charge weight. They old systems were using a volumetric charge measurement system. These cartridges also often had missing or double copper closure cups, and material flaws in the aluminum cartridge cases. We were looking to increase the production of ammunition from 40,000 units a year to close to 1 million. The solution was to have completely automated loading with net-weight, check weight systems and liner voltage distance transducers (LVDTs) to have a machine check for presence and location of these items.

Mark 19 issues mainly pertained to the timing of the feed system on the weapon resulting in dropped rounds and what we called at the time banana cartridges (because they would get bent by the weapon). Both caused feeding issues and could cause a lodged projectile or even a dropped round. The Mark19 represented new challenges to the infantry in the form of a high explosive machine gun in a small package of 65 pounds. Another issue was using the right lubrication in the field. The Mark19 called for LSAT lubricant, which was in short supply. A lot of feeding issues were based on a lack of adequate lubrication or lubrication not in the right location on the receiver rails or feed tray. Every gun coming out of the Saco factory was function fired for firing rates. If I remember right, we fired three guns 50,000 rounds each for endurance testing each year.

The bottom line was that most of the early stoppages were attributed to ammunition. Improvements to modern manufacturing methods and inspection reduced these to almost non-existent in the early stages. The weapon went through changes, as well. The cocking lever was modified to a two-piece design that reduced the possibility of an out-of-battery firing. Lubrication became more prevalent, and attention was spent on the timing of the feed system. If you had a problem with the Mark 19, it could usually be attributed to either the feed shuttle timing, a dirty weapon, or a broken part. One time I was called in to look at some weapons having issues. It turned out they did not have LSAT lube and were instead using WD40 and Break Free. They would run through maybe a box or two of ammo (32 to 64 rounds) before the gun stopped. We brought one tube with us, and we painted it on using a paintbrush to get through the training until a supply was sent in.

Over time, I was involved in several malfunctioning investigations and would try to get on-site within 48 hours. As an infantry weapon, we were not doing round counts (of how many rounds had been fired through the weapon) so we would never know what to expect, especially at training locations. I would say 80% were attributed to ammunition. If you are making over 1 million rounds a year, it is possible to get one or two bad rounds. The fuses were made back then at KDI and were difficult to manufacture but had double safeties (spin and setback). Most in-bores were attributed to a low order detonation from a round striking a stuck projectile lodged in the barrel.

Therefore, to answer your original question in the 40x53mm platform, at that time, it would have typically been the ammunition guy causing the problem.

SADJ: As an ammo guy, I will humbly accept the criticism. As far as the rest of the story, all I can say is wow! That is an amazing summary of decades of work. Over the course of your nearly 40 years in 40mm, what do you feel was your greatest accomplishment?

AP: The transitioning of the Mark19 to the Army and the rework of the technical data package. Getting it into full-rate production and fielding to the U.S. Army was a terrific feeling. Seeing what you worked on and talking to soldiers about the use of it in combat and how it saved their lives meant a lot to me. I met with some soldiers that were involved with the rescue mission of the “Black Hawk Down” incident in Somalia. The largest weapon they had available on the ground was two or three Mark19s mounted on HMMWVs. They were using it as an anti-sniper weapon and fire was directed by a captain using a laser pointer. The captain talked about the leveling of a hotel in Somalia that was stopping their rescue attempt and which they were receiving heavy fire from. The Mark19 took down the entire building. Knowing what we did at ARDEC saved a lot of U.S. lives, and knowing it was instrumental to the rescue operations, made it all come together for me. I still remember talking to this captain about what the Mark19 enabled him to do. It was hard not getting teary-eyed for him and me while listening to his story.

SADJ: Looking back over your career, was there a particularly fun project that you remember?

AP: The Extended Range Guided 40x46mm cartridge (EGR40) was the most fun. This projectile was for the handheld M79, M203, and the M320 low-velocity 40mm weapon. I was the technical expert for some time in 40mm ammunition engineering and I was asked if I wanted to lead a design team in the development of the early R&D effort. It was an easy choice going from riding a desk to getting back into a real hands-on engineering development project.

My senior design engineer, Ronny Alzamora, and I designed a new finned projectile and cartridge case with an improved combustion chamber. We had a team of engineers working on guidance navigation and control, camera, transmitters, laser receptor, and also working on wings and canards. Every week we were cutting metal and going to the range firing projectiles. It was all hands-on design work which you just didn’t usually see in the government. We had between 20 and 40 people working on various parts of it, along with a contractor and universities. We even did some early work with some students from West Point as a capstone project. We also looked at a rocket assist system. It was a lot of work. We pushed the envelope… a lot. We worked the engineers very hard. I was very lucky to have had that opportunity and it was a lot of hard work getting the separate teams focused on the end game. I learned a lot about human relationships and forming a team.

SADJ: What project was the most challenging?

AP: It was, by and large, the EGR40 because of the hands-on work we did.

SADJ: Are there any projects that you wish you could’ve had a second chance at it?

AP: What we learned about the LV 40x46mm, we never got a chance to put into practice. We found that course correction could not be accomplished in the time of flight and was not enough to make a difference at impact. We did successfully put a camera in the projectile, survive launch, and transmit and receive video and course correction signals. What we did learn was that the current 40mm round is spin-stabilized and lost spin and wobbled, making it difficult to hit a target at 400 meters. When we made our fin-stabilized projectile, we were more accurate out to 600 meters and had some variations that we were able to fly to 1,000 meters. Toward the end of the R&D project, we were pushing to drop the guidance (wings and canards) and convert to just a tail-fined projectile that had the ability to double the range of the standard HEDP projectile. We were able to increase HE and fragmentation by designing a new larger warhead. We could not get the funding to pursue this option and the team was dispersed. They tried to make improvements to the existing spinning projectile but could not demonstrate any major improvements with a spinning projectile. A finned projectile is more accurate and will fly further than a spin-stabilized one.

SADJ: Are there any other areas of your work that you would like to share with our readers?

AP:What we (Army Engineering) do has an impact on soldiers’ lives even if we don’t know about it. Don’t believe that it can’t be done. So many times in my career I was told that this or that wouldn’t work. I was told we would never get a camera to survive a gun launch. We were told we would not be able to transmit a clear image. You have to look at new innovative ideas and methods. Modeling, simulation, and design of experiments are the keys to success. You have to get away from the build-and-break mentality and think about the design of experiments. You need to test statistically with multiple variants to reduce iterative designs. Design decisions are made on statistical-based results.  

SADJ: Can you paint of picture of what the 40mm systems families will look like 40 years into the future?

AP: What I envision for a 40mm low-velocity grenadier M203/M320 weapon:

• 1-2 camera rounds with a GPS location that will transmit enemy positions back. Detect behind berms, buildings, or in defilade.
• Several extended-range projectiles with a higher velocity and flatter trajectory with increased range out to 1,000+ meters. Finned projectile with improved warhead and increased lethal radius.
• Several HE dual purpose projectiles with improved armor penetration.
• Possible netted projectile or an airburst anti-UAV projectile
• Specialty blast overpressure round for room clearing or tunnels.
• Specialty non-lethal projectiles.
• Specialty flechet round for room clearing. HEDP is useless in urban areas, room clearing, etc.
• Specialty door breaching projectile (may be able to do this with a blast overpressure).
• An improved fire control system that would allow the rounds to take on a semi-mortar-like role.

And, for the Mark19 High-Velocity system:

• A camera round that can be used for GPS and intelligence. These rounds will be able to provide intelligence out to 2000 + meters.
• An anti-UAV projectile; blast overpressure, net, etc.
• Flechet round for urban areas.
• Flare rounds, including IR flares, with higher altitudes and longer burn time. These are not currently in the HV systems. This would give night vision extended range.
• Improved cartridge case hemispherical powder chamber.
• Extended range, fin-stabilized rounds for ranges over 2,000+ meters.
• Improved fire control system to allow indirect fire applications.

Since U.S. Ordnance received the NSN and contract, there are now over 186 parts inspections that must be accomplished. Each one must meet the military standards for production. There is also a protocol testing 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 the proceedings. In this article, we’ll review relevant first parts of the testing we observed. 

Section 3.7 Marking: Each machine gun and each part for which marking is prescribed shall be clearly marked in accordance with MIL-STD-130. Each receiver shall be identified with a serial number which shall be assigned by the procuring activity. The markings in this photo are the correct ones according to the MIL-STD. The barrel markings are as well, but parts like the barrel also receive a “PM” mark for “Proof” and “Magnetic Particle Tested” (See the M249 article in this issue for Magnaflux procedures).

Finished MK19 barrels waiting for assembly. As part of the MIL-STD, the grooves must be checked for height all through samples of the production barrels. Here, an extremely thin shim is cut cross-sectionally of the middle of the barrel, and the consistency and depth of grooves related to lands are checked, as well as finish depth. The cutaway barrel is for reference on the chamber and how the projectile is entering the grooves in the bore. Obviously, these are destructive tests and done on random barrels during the specification match testing.

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 greater recoil forces than it will measure in this test. The reason for testing during the belt-pull test is 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 single rounds fired.

In the next issue of Small Arms Defense Journal, we will be joining U.S. Ordnance for the full-tilt firing part of the test. The ammo is lined up, the testing fixtures are ready, and we’ll be doing cadenced endurance testing, temperature testing, belt-pull, cyclic rate of fire, angle of fire, firing modes, accuracy, reliability, and a host of other tests. The full trunnion load test will be done several times through the testing. Be sure to join us!