ca m15a4 spr

Most games I play in allow semi auto sniper rifles (full auto must be physically disabled, like putting a small rod in the lower receiver) but the manual doesn't really help, so i have a bit of problem trying to remove the front sight because its blocking my scope. Anyone knows how to remove it? also, are there any silencers that thread directly onto the m16a4 'chipped' style flash hider?