The used MC i bought off Ebay years ago came with 3 sets of molds, all had a few issues, but nothing that made them unusable. The main issue is that the 9mm conical has been used quite a lot, there is a wear mark on the mold where the bolt that the sprue plate pivots on and i believe the sprue plate is warped a little allowing lead to build up underneath it.
When casting, i get lead building up in the groove in the mold block that pushes the sprue plate out so the bump on the back of the projectile gets larger and larger, not cut off flat with the base like it should.
My plan is to mount the cast iron mold halves in the mill and face it, so it's dead flat, i was then thinking i should polish it so it's nice and smooth, but i'm not sure if that is a good or bad plan. I was going to also make a new sprue plate and grind the back so it too is dead flat so hopefully it will not get any lead build up. The projectiles are BB and i believe there is enough material there to not cause any issues.
Is this the right way of doing it? or should the surfaces not be polished?
I hope to use high carbon steel for the sprue plate so it will hopefully last better and keep a sharp edge to cut the sprues off.