There seem to be a lot of mixed experiences with the Caldwell. A guy I work with has us 2. The first one was problematic and he actually wound up shooting it because the bullet had to pass very very close to the sensors and it had to be between 6 and 8 feet away before it would read. He messed up and put a .30 cal X bullet through it. He says the replacement he bought has not been nearly as difficult.