if you have that rifle in the multiplayer game then you have the 2.11 patch i know what you mean about the sound the only thing i would suggest is to un pak teh sound files in pak3 and see if taht cures it, it didn't for me but i've been having problems with other sounds as well.
yeah...ea didnt actually fix anything in 2.11, all they did was added the demo things, malta map, demo skins like the croc..er..british 6th skin and the gewehrgranate