A few weeks ago I finished the Sniper missions in Zombie Frontier 3 with the M21 (I managed to do this without the AWP with quite a few Adrenalin and Gold Bullet items). I got the specified silver reward, but nothing appears to have changed in the game. I was in the middle of T4 (Lab No. 9) and am now working my way through T5 (Subway).
Does finishing the Sniper missions unlock anything? Or are they just alternate missions that do not advance the gameplay?