If you want to try something else first, to get a bigger bullet try this (this is not my idea - I learned it from some other poster - I forget who):
Get some high-temp aluminum tape (at WalMart in the paint section). You can get a small roll for about $2.50. Cut out two pieces of tape about 1" long and 1/4" wide. Peel off the tape backing and put the tape on the inside of your mould, one piece vertically in front of the bullet cavity (at least 3/8" away from the cavity), and the other piece vertically in back of the bullet cavity. This tape will hold the cavity apart very slightly.
When you first start to cast with this setup, some of the tape adhesive will melt with the heat. Watch it carefully and when the leaking adhesive starts to get near the bullet cavity, stop casting, let the mould cool, and wipe off the adhesive with solvent. You should be able to get about 25 bullets before the leaking adhesive gets too close to the cavity.
The second time you cast, you will still probably get some leaking adhesive. But by the third time, everything should be OK to cast for as along as you want.
Your bullets will be about .001" larger in diameter. You can go even bigger if you want (.002") if you put four pieces of tape in the cavity. Just put the other two pieces directly across from the first two, so that each piece of tape bears on another piece of tape when the mould is closed.
This works great!
