just my 2 cents. putting a loop on should not affect your group unless you didn' t measure and place the nock back in the original position. if anything it would only change your up and down not left or right. I think the left or right variance could hand torking the bow. You might try paper tuning to see what your arrows are doing, remember that even paper tuning will show hand torking the bow. too much grip will cause the left and right variance. hope this helps.