Pure silver melts well above 1600 deg. F. Most alloys have lower melting points but even silver solder, only 56% silver, melts at over 1100 degrees.I mean to double-check this, but I have no reason to doubt it. Good to know.
So you are not going to cast silver bullets with an 800 degree lead pot and iron molds. As the guys at GW put it, Tonto sure didn't turn these things out over a campfire. It takes jewelry equipment and techniques.
Here's another forum on the same topic, and some useful craftsman's details for future reference.