Also there is only so much metal going in, and coming out of the strike.

Unless a portion of the die is added to the coin, the weight will be the same. Nothing added to the coin, but the strike. So chances are there will be no excess metal. A large
Cud, die chips, mintmarks, does not affect the weight. What goes, comes out the same weight 99.9% of the time. The metal is distributed to fill out the coin. When the planchet is under weight, the devices show this lack of the metal for the planchet. What goes in, comes out, with the same weight most of the time.