Glad to know who designed the Boolit!
It fits my Finn M39 and Long Branch .303 No. 4 Mk1* perfectly, but I ordered mine with a 0.09" bevel base at 7-1/2 degrees which I want to use as-cast and unsized, .316" from my mold. I am running 1/2 charge of normal extruded tubular powders 18-20 grs. of 4064, RL15 or Varget with 1.0 grain Dacron loose fill, looking at 1300 fps +/- works for me.