I have a swiss K-31 carbine and i am re-finishing the stock. Anyways, my question is this where is the tang screw and the reciever screw. I was told if i lossened both up then torqued the recever screw all the way down, then tighten the tang screw all the way minus 1/8 turn and played with the tang screw + or- i could tighten or widen my groups. I tried finding plueprints on line but no luck. right now it shoots 3" groups at approx 100 yards open sights