Frustrating! - Magnetospeed Sporter Barrel Mounted Ballistic Chronograph

First off, the unit is very difficult to strap on tightly to the barrel. It moves back and forth between shots and you can get 200-300fps variations! Second, you will waste lots of ammo trying to correct the various error codes that pop up for no reason. Correct one error, and another pops up! I burned through 30 rounds and gave up. Couldn't trust the 4 readings I did get off of it. A wasted hour at the range. Oh well, at least the scope got sighted in!