So I'm looking at the shapeways site, and still not really sure which models to get. I'm trying to figure out which ones would fit a SN582 Ruger 5812, which is essentially the LEO police carbine; a tactical model but with an 18" barrel. The other one would be the normal 16" tactical model, 583, so both have tapered barrels. Anyone help me with the correct ones? Also, whats the best finish option to match the barrel (factory bluing). Looking for the "pin on" model (no sight, lug only) that would use an M16 bayonet. Thanks in advance!