As mentioned, a string loop helps to evenly distribute force above and below the nock itself so you get more of an even distribution of energy upon release. This should, theoretically, improve accuracy. I switched to a loop at the end of last season and saw an instant increase in my accuracy level. However, I used what is commonly termed a " low loop" where the arrow is actually nocked above the top knot of the loop and a served-in nock is used instead of a brass one. This would seem to go against the theory that the equal force distribution alone was responsible for the increase in accuracy. I would like to think that Ausie' s suggestion of a crisper release may play a part in it.