Shooting my buddy up, after about 10 shots in many hours, I hit him in the usual spot, but no blood registers, until I pull it out it flashes but won't register when put in spot where it flashed.. I see the vein pushing his skin so I have to be Right there.. Wtf. Done this 100 times to others and have never had to go more than twice. I tried 10 times at his request before saying no.