It can be done. It's been done fairly often. Successfully is another matter.
There are magazine articles on it. Lots of material to be found with Google and some at Castboolits. For giggles see Lone Ranger Go Away by Jack Lewis from the April 1964 edition of Gun World in the middle of the last century.
Using strictly lead equipment and temperatures flat doesn't work. For a one off try a torch but don't expect it to work. The Lone Ranger could not have done it with portable equipment let alone over campfires.
Silver's melting point is way too high for a lead pot - needs foundry equipment to get maybe 2000 degrees and when you're done with a lead bullet mold the bullet is way under size and too hard to upset and obturate. Mostly looks wrinkled and often cools too quickly and in zones. Like zinc diecasting metal - pot metal - a pointed design like the Lyman 356402 just might give good penetration on steel or body armor.
As you say jewelry equipment or plating or finding one of the old Railway Express marketing silver bullets or machine one.
