User blog comment:39658/Unknown Weapon?/@comment-1932315-20130603053712/@comment-1932315-20130603073544

I just picked that exact one up (Dead CIty, in the shower), and it's a Preved (just look at the gallery on the Preved page). Preveds also aren't side-loaders - those are Valves.

Edit: What may be aiding in your confusion (it certainly did when I just fiddled around with it the first time a few minuites ago,) is that you can never buy Preved ammo, not even at Depot. The sniper ammo in your inventory is for the Valve and is smaller than the anti-materiel rounds for the Preved.