Hi Paul,
Theoretically, Delft clay could be used for anything normally cast in sand. However, at the scale of trigger guards and buttplates I think the clay would be much more expensive than using sand. You could easily build casting frames for projects as large as buttplates and then use sand or clay depending on cost. The Delft clay really shines (over sand) when you want to cast small objects that have a lot of detail. It is almost ( the important word here is "almost")as good as investment casting with respect to maintaing the details and much better than sand. The Delft casting kit costs about $86 from Rio Grande Jewelry supplies and includes a small casting frame, about 4 lbs of clay (enough for a lot of castings), and an instructional CD. You need to get a melting crucible with handle, borax flux, a heating source, and the means to prodce the models. If you make your own frames, which you need to do if you want to do anything larger than a wrist escutcheon plate, you can just buy the sand at $48 per 4 lbs bag. Certainly, sand should be a lot cheaper but won't retain the details.
dave
