I think the people that have heads that don’t open are trying to shoot a bow 30000000 fps so they shoot s super light arrow. After they don’t get penetration and they find the arrow that falls out of the entry hole and the blades aren’t fully opened they automatically say head didn’t open. Forward momentum in conjunction with hitting a given target opens the heads and keeps them open. Once forward momentum stops then the blades can move around especially when pulled backwards like when they fall out of a deer. I’m with Todd ive literally shot hundreds of heads and never had one fail. I also make sure to check each head prior to shooting it to make sure whatever mechanism it has that makes it operate isn’t messed up. I shoot a pretty heavy arrow pretty slowly and have blown through some big bodies deer. Ive shot through shoulder. Heck i shot one nearly from end to end one day on accident. I have lost some deer but I have never felt it was the heads fault. I think that’s just a cop out.