Yeah, that PTRS is my favorite sniping weapon in CoDW@W (even though the real thing, they say, would have been wholly unsuited for sniper duty)
There was a Swiss Solothurn 20mm for sale in Shotgun News a few months ago.
Pity I didn't have the ~$18k (best I recall, that's what they wanted for it) lying around.
For your amusement:
http://www.youtube.com/watch?v=n4Dea...1&feature=fvwp