I have to say I agree with cajun I myself don't use mechanicals just becouse muzzy's always work for me and I don't see a reason to change. I have done some of my own reasearch on mechanicals and most of the newer styles are good broad heads some styles it is even impossible for the blades to not open. From what j wag say's I too believe that some thing happend that caused that arrow to fly bad and have poor penetration he stated that he did draw and then let down and this will some times cause your nock to come off the string. In this case it sounds like the problem. Next time make sure you check your nock if you draw and then let down.