I was reading about miniature guns (http://home.comcast.net/~boburso/piccolo/) that fire "2mm pinfire" blank ammunition. They're really cool, but the cartridges seem to be hard to come by. Would it be possible to make your own by dissolving the lead styphnate in primers and then precipitating it in homemade cartridge cases?

Yes, it's possible to dissolve lead styphinate in acetone. But, take care, lead styphinate has VoD about 5000 m/sek, it's not the gunpowder (which has about VoD 300 m/sek). So lead styphinate stresses your barrel much more. Do not put much, or your gun will explode.....