For those who haven't tried, sniping has been nerfed, one of my main gripes about this game. You almost never score a one hit kill, even with the PSG1. However, the PSG1 sucks in general (I can never hit anyone with the crappy scope), so it's best to fall back on the Semi-Automatic. The WA2000 is the best by far, but only if you can hit the target twice. It also doesn't help sniping that you cannot carry some sort of machine pistol or something like that instead of relying on handguns. If you run it, go with Akimbo Pythons for instant kills aplenty.
And QuickScoping is somewhat there if you're hella good, heh.
But really, stick to Assault unless you can work with the Sniper conditions.