James,
Generally, with all nose shapes, hollowpoint works the best. Flat nose and round nose are close, but the edge goes to the hollowpoint.
As far as base shapes are concerned, the best seems to be the flat base. The cup base, and rebated boat tail sometimes equal the flat base, but tinkering with the weight. Probably something to do with center of gravity, and balance.
It seems that ANYTHING made with a hollow base, like an actual pellet, is absolutely useless. If any out there decide on a Corbin setup, pass up a hollow base punch, you'll just be wasting your time. To give a quick visual, I shot 15 grain hollowbase slugs at a 10 inch plate at 30 yds. Only 4 out of 10 hit it. Change to flat base, same weight, all within a nickel. Same velocity. Not great, but night and day.
Hope this helps, any other details or info you would like, please feel free to ask
Tom Holland
Field Target Tech
Fieldtargettech.com