Speer response:
for the 500 S&W with Lil' Gun, we used a Federal 215 primer: Start with 45.0 grs @ 1667 fps to a MAX of 49.0 grs @ 1739 fps. Tested at a COAL of 2.070"
Seems a bit high. Asked them to confirm since this higher than Hornady 300 gr FTX for Lil Gun.