Does anyone know what diameter bullet 86gr. fmj I need to buy to reload a 7.63 broom handle with.

Ditto for a swiss 30 cal luger

Most the groove diameters on those two pistol mic around .311. The .308 bullet will be a tad small but they will still work thought as long as your expander plug doesn't open the case mouths up too much. I believe most the bullets you look at will probably be .310. The bores vary a lot from gun to gun and brand to brand. A good crimp die is one that LEE makes specifically for the 30 Mauser/30 Luger. It's different from their factory collet crimp die for rifle cartridges. There's not much of a neck on either of those cases. Myself I shoot cast bullets from them.