Somewhere on the forum I read about someone doing this. I believe it was Larry Gibson in a thread on 45/70 collar buttons or round balls.
Either way it’s a pretty cool and simple idea.
Place a gas check into the driving band of a mould half. Close the mould.
Now pour your bullet.
You can customize a smaller wadcutter from any mould this way. I imaging if the gas check is placed upside down that you could basically just use it as a spacer and re use it again. Or place it right side up and you have your gas check already seated onto your new wadcutter.
Why you ask? Why not? I’m going to mess with this to make some 458” wadcutters to play with in my 45/70s.
Seen here with a Lyman 358495 mould and hot glue (lead was cold by the time I remembered to try this)