I am going to use my O/U shotgun this year for closeup deer work. I started with a .690 RB of pure from a lee mold. Pound it through a Xtra full 12 ga choke tube, this gives me .685 around the equator and two flat poles on the RB. I hot glue on a plastic cup. Take a WAA12F114 wad and cut out the collapsable area. Glue the wad and gas seal back together. then load over 36gr of bluedot and fold crimp. Off hand I got 6" @ 35yrds and 1150fps for this 520gr ball load.
Attachment 16821
Attachment 16822
1527 ft/lbs @ muzzle 961 ft/lbs @ 100 yrds