Making the Army’s “Greatest” Machine Gun

The Army recognized the M240L 7.62mm Medium Machine Gun among the 2010 Army Greatest Inventions (AGI) during an October 11 awards ceremony at the AUSA Annual Conference in Washington, D.C.  The Army’s first titanium machine gun was in good company, sharing the limelight with no less than five other Picatinny AGI winners out of a field of 10 honorees.

“The recognition validated the value the gun delivers to Soldiers,” said Tom Walsh, M240 Product Director, Project Manager Soldier Weapons. “The M240L is five pounds lighter than the original M240B, but delivers the same performance and reliability. The weight reduction means a great deal to Soldiers who are carrying the guns up and down the mountains of Afghanistan every day.”

M240L "Army Greatest Invention" Team Takes the Stage at AUSA. Pictured from left - Ms. Heidi Shyu, Acting Assistant Secretary of the Army for Acquisition, Logistics and Technology; Dr. Geraldo Melendez, Director, ARDEC; LTC Thomas Ryan, PM Soldier Weapons; Tom Walsh, PM Soldier Weapons; Jean-Louis Vanderstraen, President, FN Manufacturing; Chris Mahony, ARDEC; Joe Chiarolanza, ARDEC; MG Nick Justice, Commanding General, RDECOM

Project Manager Soldier Weapons fielded the first M240Ls to dismounted Army and SOCOM units operating in Afghanistan for an operational assessment in January 2010. “First Unit Equipped” (FUE) took place at Schofield Barracks in Hawaii in November 2010. The Army took delivery of more than 3,600 M240Ls, 1,700 of which were fielded in support of current or upcoming Operation Enduring Freedom (OEF) deployments. Getting the program to where it is today was an enormous challenge, but one that Armament Research, Development and Engineering Center (ARDEC) and Project Manager (PM) Soldier Weapons personnel were more than prepared for.

 

Making it Lighter without Making Compromises
The M240 7.62mm medium machine gun series has long been a dependable workhorse. The Army first adopted the weapon in 1977 as an armor vehicle mounted secondary weapon system. Army and Marine infantry units began employing the M240G and M240B in the mid 90s. The popularity of the gun soared as it became known for reliability, durability and low maintenance requirements. Despite its success, Soldiers still pointed to the added weight and length of the M240 as compared to its predecessor, the M60.

PM Soldier Weapons and ARDEC engineers opened a dialog with the manufacturer to consider ways to reduce the weapon’s weight while preserving all of the performance standards of the original weapon by 2000. On this point there could be no compromise. The organizations collaborated to develop a variant of the M240B that would reduce the weapon’s weight by four to seven pounds without compromising the gun’s operational characteristics and outstanding reliability. Engineers started evaluating high-performance, lightweight materials and alternative manufacturing methods to achieve this objective.

Going “Space Age”
Initial studies made it clear that the engineers needed to incorporate metals other than steel if they were to meet the weight reduction requirement.

“You have to be careful when taking away or substituting metals,” explained ARDEC mechanical engineer Kevin Bauer, who worked on the M240L during its development. “Thinner metal parts have higher stress and may be less durable than the original parts. The team opted to preserve the integrity and strength of the M240’s steel operating system components while leveraging lighter weight titanium in other parts of the weapon.”

Known as a “space age” metal, titanium is especially known for having a very high strength-to-weight ratio. The new titanium parts on the M240L include the receiver body, the front sight post, and the carrying handle.

Working with titanium called for adjustments to the manufacturing process. The lighter weight metal takes longer to machine than steel and requires more frequent replacement of tooling bits. Engineers sought early on to prove out the feasibility of using robotic welding, but ran into warping issues. The final solution rested in using stainless steel rivets, which are more pliable than titanium and resist corrosion when in contact with titanium.

The weapon needed a protective coating after assembly to preserve the metal. Steel weapons typically get a phosphate coat and are subsequently oiled, but the titanium receiver required a completely different process.

“Titanium alloys don’t actually rust, they gall, causing the surface to become rough and deformed over time,” explained Walsh. “To solve this challenge we researched coatings that could protect the metal under extreme operating temperatures. We found success with both boron and chrome carbo-nitride coatings used for industrial, high-heat applications. A ceramic-based top coat is added to complete the process.”

Once Army engineers were satisfied that the weapon’s manufacturing process met the grade at an acceptable cost, the “real” tests had to be proven out by Soldiers themselves. Army Research Laboratory’s Human Factors Engineering group set up Soldier performance studies at Aberdeen Proving Ground to determine whether the Soldiers responded well to the new design.  Soldiers carried the M240L significantly faster than the M240B on the cross country course and turned in improved completion times in obstacle course runs as well. Soldiers also rated the majority of the mobility and user acceptability characteristics for the M240L significantly higher than the M240B. The results demonstrated that the final engineered product was a success where it mattered most – in the hands of the Soldier. 

Aiming for the Future
The titanium M240L Soldiers use today represents a leap in weapons technology inspired by Soldier feedback. The lessons learned from this program will undoubtedly benefit future weapons systems that will maintain our continued advantage on the battlefield.

Enhancements to the award-winning M240L design are already underway. The M240L will be fielded with the short barrel and collapsible buttstock in spring 2012, which will reduce the gun’s overall length by up to seven inches (four inches alone with the short barrel) and bring the weapon’s weight down to just 21.8 pounds. The collapsible buttstock will be available by late summer for the M240B, as well as an adjustable bipod.

 

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