In particular, the effect on pressures and internal volume of different wadcutter boolits.
I have recently seen a couple of people make what I believe is a mistake about necessary powder charges for standard target wadcuters when changing from a hollow based wadcutter to a solid wadcutter.
Specifically, a wadcutter loaded flush with the case mouth and crimped in place in both instances.
The idea was expressed that there would be less pressure from a solid wadcutter so loaded because the boolit is shorter than a hollow based wadcutter which would be seated deeper inside the case. I believe this to be in error.
In both instances, the boolits are flush with the case mouth. Both boolits weigh exactly 148 grains. There is exactly the same weight of lead inside the case in each instance. Both boolits would displace the same amount of water if dropped into a glass. Assuming the same alloy for each boolit, the solid volume of each boolit would be the same because they weigh the same.
The only reason the hollow based wadcutter base is farther into the case is because of the hole on the back end of the boolit. Even though the base is deeper into the boolit, the hollow in the base allows for the same internal volume for the cartridge as a solid boolit. There should be no difference in pressure due to the boolit other than a possibly tiny amount due to a longer drive band area. I would expect this to make little difference in pressure during firing.
If there is an obvious error in my reasoning, please educate me.