Насчет М14 не искал. Знаю, что с винтовкой DMR USMC используется сапрессор:
DMRs utilize the traditional M14 muzzle device; however, since deployment in Afghanistan in 2001, some DMRs have also been equipped with OPS, Inc. 2-port muzzle brake, threaded and collared to accept an OPS, Inc. 12th model sound suppressor.

http://en.wikipedia.org/wiki/U.S._Marin ... sman_Rifle
http://www.opsinc.us/