Turned a 30-06 Rem700 barrel down to fit into a 12ga handi barrel on an SB-2 frame, leaving the profile of a 3" 12 ga shell on the chamber end, then cut the chamber with the 30 Gibbs reamer.
Chamber's rough (a couple places where a chip obviously got stuck between the flute and the chamber wall) will do better next time I use the reamer.
Loaded up 22 pieces of brass with LPP, Hodgdon Clays, Paper Towel, Corn grits, compacted with 3/8" stationary drill bit, then topped with wood glue.
Let dry overnight, then made lots of popcorn-smelling smoke with little poofs of paper towel in the pasture....
Nicely formed brass. I didn't cut the chamber as deep as the drawing above suggests; other sites/diagrams suggest a case length in the ~2.464" range.
Now, for those 147gn FMJBT j-words I got from Top Brass at the last show for... what was it? $0.12-$0.15 apiece, as I recall.
Here's hoping I can hit 2950-3000 FPS.... Candidates for powder include Alliant 4000-MR and Rel-17.