I have used both fixed and mechanicals and both have performed well. Every deer that I have hit with a mechanical head was a pass through and has dropped within 40 yards. As far as target practice, both Paul and Bees have good advice. I have looked at the Spifires after going through the target and they were closed. I figured out the braking force on the shaft was slamming the blades back into the closed position. I could see foam under the blade. The Scorpion XP's use an O-Ring so it is pretty evident that they opened. With any design you use, you must clean them after every shot or else the foam will build up and jam the blades. As was stated previously, always check your mechanicals to make sure that the blades move freely.

After saying all that, I started bowhunting with the Thunderheads, went to mechanicals and now I am using the Wasp Sharpshooters because I like the cut-on-contact blade design. I'm sure next season a new design will come out and I will try that. I just like to fiddle with new stuff.