You didnt mention caliber, so I'll assume a.50.I'd begin with either .430 or .452 caliber Hornady XTP's in 240 grain( .430's) or 250( .452's) and modest charges of Triple 7( loose powder).As far as sabots I've had my best results with Harvester brand.My Omega Z5 shoots 3 shot 100 yard groups of 1 inch or less with regularity, with a .430 240gr XTP in Harvester sabots over 70gr 3f Triple 7. Velocity is 1725 fps.She does , however, get spooky with the .430 300 gr XTP , same sabot, over 80gr 3f triple 7. 1660 fps and her smallest 3 rounder at 100 was 3/16 inch center to center. One of the most important things you can do for best accuracy is to clean the bore between every shot.Good luck.I'm here if you need more help.