I have been playing around with the Gauss and Reflex Sight over the last couple of days. I have accrued 100 kills but I haven't received an attachment unlock. Strangely I now have 7 unlocks available in the SCAR tab but I have everything already unlocked for that weapon. I also keep getting various achievements such as 'VOYEUR' over and over. I would also like to unlock the C4 but can't remember if this unlocks at a certain level or whether you have to complete assessments for the other explosives.

C4 Can be unlocked at the same level as the Gauss rifle. So tough luck.

Okay thanks - or no, how about **** off.

I would also like to unlock the C4 but can't remember if this unlocks at a certain level or whether you have to complete assessments for the other explosives.

I just said what I knew, because it's been way too long since I last unlocked an explosive.
And the only hint I have in my head is that they supposedly use weapon unlocks.

P.S:

chill the **** off.