I did the same thing. ^^ Look at the name of the gun, and the different ammo types list all the guns they will work for. It's the pale blue 3-pod thinger.
The lvl 10 guns you can buy are duels, I want them!
Quick question, that's semi-on topic:
There's only one PT thing for bows and guns, right? As in, you're as good with bows as you are with guns? Or do they have different things?