The formula is easy for above average shooting.
A good trigger job , I like 3 1/2 -4lbs on a big game rifle and go to 2 1/2 -3 on a varmit rifle. Good confortable bench where one can sit naturally without having to be a contortionest to nestle into one's rifle. Good sandbags for front and rear of gunstock. Precision site in 100 yard targets , you know those diamonds so crosshairs can be held with the expectation to be in the same place for every shot. Good ammo loaded with a minimum variance in FPS.
At this point a little talent of the shooter's part helps. Gently apply pressure to trigger and don't forget the follow thru. Yes , there is a follow thru even in shooting a rifle.
I've got a few rifle that give one hole ragged groups when I do my part. Just ask George Gieges gunsmith at Dunkleburgers in Stroudsburg Pa. if Kevin has some one hole rifles. Other references on request if needed.