Metal casting question.. any metals offer 1:1 casting size?

[Propsjonnyb]

You said in your post that you had the original mold , what is that mold made of?? and what was the original cast - metal or resin , unless the silicon or casting compound is high temperature , I wouldn't suggest casting in hot metal as the mold will heat up to the temperature of the casting metal and that can be over 500 degrees F so you 'll need special equipment to handle let alone thinking about shrinkage Pewter or tin based alloys are best for low shrinkage less than 1%

 

[Propsjonnyb]

Lead free pewter and a platignum high temp silicon would be my suggestion , I have hot metal cast large pieces before , rifles ,machine guns , hand guns , done properly there is very little shrinkage and I can get nearly a 1:1 copy if I break a large piece into its component parts and cast separately.