Why can't it be pushed out from the breech face w/a small dia rod through the firing pin hole?
Unless I'm missing something, the firing pin hole in the breech face will have to be plugged anyway to keep the cerrosafe from draining right through as you pour it in the back end of the cavity.
Just put a piece of masking tape or DucTape over the firing pin hole on the breech, or clamp a smooth piece of wood up against the hole to block it.
Pour the casting, let it harden a few minutes and push it out from the face of the breech.
Don't let it set in the action till it gets room temp. The stuff will have expanded back to full size and have locked itself in place then and you'll have to heat it up and melt it out and start over.
While it's still warm/hot but solidified,,the material is something like 5% smaller than the actual cavity it is casting.
It returns to full size when cooled. That reduction in size allows removal w/o damage to the casting.
Warm up the frame a little too before you pour in the cerrosafe. The casting will be smoother and more complete w/o wrinkles,,just like bullet casting but you're only dealing with 212F material instead of 700F lead.
