Melee damage/Single target auto fire v1

[Caradhras]

A couple of basic questions from the V1 rules.

During play a few issues from my players...

1. One elite PC sneaks up on a sentry and jumps him, using his combat knife he does a specified head shot and hits..... he rolls 2d6 (average 7) and the sentry shouts 'ouch' and isnt dead!

My thoughts for a solution is give the player an auto-kill if he has succeeded in surprise and hit? This situation aside - melee damage does seem a bit feeble tbh.

2. The players are being assaulted by a large group of NPCs whilst dug in - they have a PK and an M-60 with the rest armed with M-16s and the like. The V1 rules only allow 1 target per round whereas they should be cutting down considerably more - is there a good rule for this I can lift from another source?