And no, it's Not a silenced sniper rifle.
Just a tip.
In missions where you have a sniper rifle and a silenced pistol, sight the enemy using your sniper rifle, then press the use last key to switch to the silenced pistol.
Fire 2 or three shots to kill the enemy and his mate next to him is none the wiser
Thats what i usually do in Sniping mission. BUT!...it works well on Non-moving target, like in the watchtowers. For the rest, its a bit difficult, specially on night missions in which u cant see well. Most of the time i just snipe the guy in watchtower with sniper rifle, and if they try to look for me, i usually hide or ambush them.