I've tried it with the KAR and the sniper rifle. I think I actually did better with the KAR, but I still have not gotten through it. I was loving the game, but I'm stuck here. I'm wondering if there is a panzershrek somewhere that I'm not seeing??
I FINALLY finished this task. It was actually watching a show about sniper school that helped me to finally get through it. The guys kept saying "one shot, one kill." I realized that in the excitement of all of the action, I wasn't taking the time to get a good shot. Once I started doing that, coupled with noticing the last two guys come one from the far left and one from far right, I was able to complete it. It took me so long that I was actually shocked when the "objective complete" text came up.
I've been at this for 2 nights now...!!! Can anyone give me a HINT as to how to get thru this nasty bit...?!?!?
It's important not to use to much time to establish a sniperposition upstairs. I did the first time and was not able to kill all before "Mission Failed" appeared. After backtracking some saves and rushing upstairs I had ample time to kill'em all :-)