http://shop.reedsammo.com/Sub-Caliber-P ... er_c84.htm
Perfect for some of you crazy wildcatters!
I'm thinking a wildcat .50BMG necked down to .10" should punch a 7.5gn bullet pretty quick
Should be easy enough to ream a throat to pick up the case mouth in a ten-caliber barrel, turn it down to half-inch OD and slide it up a .50BMG barrel.