built up and 300 Ultra from and 300 SPS . an houge stock with bedding block , Timmy trigger. teflon coated it and installed a muzzel brake . I had it shooting .63 at 100 yards with federal ammo bearclaws ,180 andit shot 180 XXX federals .68 100 yards . I ahve shot 40 target rounds thru the gun . and one deer . It has swarovski 4X12-50 BT scope which has been very accurate to 500 yards . Gun has been cleaned after each time shoot no copper build up in barrel , now my accuracy has went to crap . 1 1/2 " at 100 , also have checked FPS of AMMO and its within 35 FPS . Not sure what happen any help would be greatful . not sure where or what to check next ? any help woudl be appricated .