Research and Development on Coextrusion of Bimetallic .220 Swift and 25mm Gun Barrels
Final rept. Jul 1970-Oct 1972
BATTELLE MEMORIAL INST RICHLAND WA PACIFIC NORTHWEST LABS
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This was a research and development program on lined gun barrels directed toward selecting desirable barrel and liner material combinations which will increase the life of barrels in rapid fire gun systems and developing the fabrication processes for producing these barrels with a metallurgically bonded liner. Coextrusion was used as the method for producing the lined barrel stock. The program was divided into two parts with the first part directed toward producing lined .220 Swift barrels of selected material combinations for testing in the M-60 gun. The second part was directed toward producing a test quantity of 25mm barrels for testing in the GAU-7A Gun System using the best material combinations and the fabrication techniques developed in the first part. Coextrusion was used as the method for producing the lined barrel stock. A-286 steel was selected as the barrel material, and TZM, Mo-0.5Ti, L605, Ta-1 OW, and T-222 were selected as the liner materials for the barrels. All the liners coextruded with the barrel steel satisfactorily over a small mandrel except T- 222. The four successfully coextruded combinations were fabricated into .220 Swift barrels with swaging being used to rifle the barrels. The A-286 steel with a L605 liner was selected as the most promising combination for the 25mm barrels. The lined barrel blanks were produced by coextrusion on a 3850-ton press using a mandrel. The coextruded blanks were fabricated into GAU-7A barrels using machining to produce the GAU-7A gain twist rifling. Swage rifling over a mandrel cannot be adapted to produce gain twist rifling.
- Fabrication Metallurgy