I put it at the base Rich, with enough compression of the 860 to hold it there.  I put the booster in the middle of the IMR7383, because the load it was intended for has a flash tube and a primer stronger than the regular 50BMG primer.  When you get that stuff to burn like it's supposed to, meaning without flame, it works real good too, but weighing three charges for each load is a bit of a pain.  I'll get some more 860 while up to Camp Perry!  That 160 should make you a good load.  If you have access to a chronograph, be sure and report the speed attained, and what sort of accuracy you get.