So a friend and I were shooting his new 416 Rigby in a CZ 550. The Hornady DGS and the DGX both shot about 1.5" @ 100yds. The he tried some of his reloads with the 400gr Nosler Part. RL 22 and IMR 4350 with 2 different charge weights each. All these loads were within specs and popular suggestions for 416 fans. They all shot 3". And last he shot the Federal with the 400gr. A frame. All 3 bullets touching. I shot a 416 Rem and it shoots everything very well. Any suggestions?