die hard beat me to it. The double bull guys use them, and on the video they decap 3 birds. If you use the straws that come with them over the blades, they do fly good. Personally though, I don't like them, and for a couple of reasons. What happens if you shoot low and hit the bird in the body. You will most definetly wound the bird. Getting very little penetration. If you miss altogether, no problem. Also, in Missouri, the head has to be intact until the butchering process. If I were to decap one, I would be in violation of MO law.
If you ask my honest opinion, I say go with a good, big diameter mechanical head for turkeys. They have a small vital area, so the large diameter is needed for maximum damage. Also, they burn alot of KE and hopefully stay in the bird to keep him from flying off. Just my 2 cents.