Re: cant find a good 313 casting mold
If your casts come up at .312 after having allowed to shrink for a couple of weeks depending on your alloy you have a couple of easy options to help to bump them up to .313 or slightly higher, maybe .3135 ..... one would be to add additional tin to your alloy and the other would be to lap your mould . This is best done when you cast a couple bullets from a harder alloy with a good tin content to make for the largest potential diameter and hard enough to do the task . Get your self a small tube of valve lapping compound from the auto parts store to start as is the best or if you have bore lapping cream it works too. Get your alloy melted, take a 1/4 hex nut, swing the sprue plate on your mould to the open position and place the nut over the bullet cavity. Now pour your alloy through the nut allowing a heavy sprue puddle to form on top of the nut and cool thoroughly. Now gently remove the lapping slugs from the mold. Take small amounts of the lapping compound on a toothpick or whatever and put a small amount into each of the driving band grooves in the mould. Gentlly place the lapping boolit back into the mould and lightly squeeze it back together loosely not too tight. place a wrench or socket driver of any tupe over the nut and start turning it and slowly over time increase the pressure on the handles until the mould eventually closes completely then give it a few more turns for good measure and is ready to be cleaned. You can repeat this with a new slug as they smooth out faster than the mould unless the mould is aluminum .