Processing of Composite Gun Tubes with GLEEM and Hammer Forging

Abstract

Refractory metal liners have been shown to extend the service life of gun tubes a considerable amount. The major technical hurdle to date has been keeping the liners in place during firing. To address this problem, composite gun tubes made of steel and pure niobium have been fabricated through a combination of the GLEEM (gun liner emplacement with an elastomeric material) and the hammer forging. The three barrels made by this approach were test fired in single-shot and burst-fire mode. One of the barrels whose liner had been cold-sprayed with tungsten carbide particles before the GLEEM process showed no liner movement in any of the tests. The success of this new liner processing technology to prevent liner movement offers the potential for further investigations of refractory metals that are more suitable as liner materials.

Fabrication and Tests of M240 Machine Gun Barrels Lined with Stellite 25

“…This was the same load that was used to process the niobium liners. 7 A picture of the test fixture is shown in Fig. 3.…”

“…At the facility, the barrel blanks were hammer-forged and machined into the final M240B configuration (complete with handle, flash suppressor, and other hardware). Some machining difficulties were experienced with the niobium-lined barrels 7 that were processed in the same manner. This was not the case with the Stellite-lined barrels and 2 useable gun barrels, which were provided to ARL.…”

“…[1][2][3][4][5][6] This process, known as Gun Liner Emplacement with an Elastomeric Material (GLEEM) has been used, along with hammer forging, to emplace niobium liners in M240 machine gun barrels. 7 The combination of GLEEM and hammer forging produced a composite barrel whose liner stayed in place during an aggressive firing schedule. However, the niobium liner experienced a significant amount of wear.…”