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Soldiers play key role in fielding lighter machine gun

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The Army recognized the M240L 7.62mm Medium Machine Gun among the 2010 Army Greatest Inventions (AGI) during an Oct. 11 awards ceremony at the Association of the United States Army 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."

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" 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 (Afghanistan) deployments.

Getting the program to where it is today was an enormous challenge, but one that the Armament Research, Development and Engineering Center (ARDEC) and Project Manager (PM) Soldier Weapons personnel were more than prepared for.

Lighter without 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 using the M240G and M240B in the mid-90s.

The popularity of the gun soared as it became known for reliability, durability and low maintenance. Despite its success, Soldiers still noted the added weight and length of the M240 compared to its predecessor, the M60.

PM Soldier Weapons and ARDEC engineers started discussions 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. In hindsight, the effort took longer than anticipated.

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.

Going "Space Age"

To achieve this objective, engineers started evaluating high-performance, lightweight materials and alternative manufacturing methods.

Initial studies made it clear that the engineers needed to use metals other than steel to achieve weight reduction.

"You have to be careful when taking away or substituting metals," said Kevin Bauer, an ARDEC mechanical engineer 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 required adjustments to the manufacturing process. The lighter weight metal takes longer to machine than steel and requires more frequent replacement of tooling bits.

Early on, engineers sought to determine 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 also 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 performed and assessed by Soldiers themselves.

The Army Research Laboratory's Human Factors Engineering group developed Soldier performance studies at Aberdeen Proving Ground, Md., to find out if Soldiers responded well to the new design.

Soldiers carried the M240L significantly faster than the M240B on the cross-country course and turned in shorter completion times in obstacle course runs.

Soldiers also rated most 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 that Soldiers use today represents a leap in weapons technology inspired by Soldier feedback. The lessons learned from this program are expected to benefit future weapons systems designed to maintain continued advantage on the battlefield.

Enhancements to the award-winning M240L design are already under way. The M240L will be fielded with the short barrel and collapsible buttstock in the spring of 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.

M240L Specifications

(short barrel and collapsible buttstock)

• Caliber: 7.62x51mm NATO

• Weight: 21.8 lbs.

• Length: 44.5"

• Max Effective range: 1,800m

• Fire control: safe, auto

• Operation: gas-operated

• Receiver life: 50,000 rds (minimum)

Article by Kevin Doell (AMC)