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PRODUCT IMPROVEMENT TEST OF SUBMACHINE GUN, 5.56-MM, XM177E2
Final rept. 1 Aug 1967-15 Apr 1968
DEVELOPMENT AND PROOF SERVICES ABERDEEN PROVING GROUND MD
Pagination or Media Count:
A product improvement test of the 5.56-mm submachine gun, XM177E2, was conducted at Aberdeen Proving Ground, Maryland. The product improved components of the test weapons were chrome-plated chambers, buffer, 1-12 inch increased barrel length, delrin charging-handle latch, hand-guard slip ring, cadmium-plated slip ring spring, shot-peened upper and lower receivers, nylon coated buttstock and release lever, and grenade launcher spacer for attaching an XM148 grenade launcher. With the exception of the delrin charging handle latch, durability of all the product improvements was satisfactory throughout the test. The chrome-plated chambers demonstrated improvement over nonplated chambers in reducing failures to extract and the hand-guard slip ring offers advantages over the previous design in ease of assembly and disassembly of hand-guards. Kinematics studies showed that the energy-absorbing characteristics of the urethane end cap on the buffer are subject to change under repetitive impacts, causing undesirably large variations in cyclic rate within a burst. Progressive build-up of fouling in the flash - sound suppressor during firing tends to increase muzzle flash and sound level and apparently has an adverse effect on bullet stability and flight. It was recommended that further development of the XM177E2 submachine gun buffer and noise-flash suppressor be accomplished, that the delrin charging handle latch be considered unacceptable, and that the remaining product improvements under test be considered suitable for use on the XM177E2 submachine gun and, as appropriate, the M16A1 rifle.
APPROVED FOR PUBLIC RELEASE