Had to send mine back. Had to have the muzzle close enough to give it powder burn before it would reliably trigger. Sent it back, apparently too much packing around the microphones. I’ve tested it with 9, 40, 556, 6.5 and 308 since then. Triggers everytime with muzzle 6-10 inches away. Use a straw to help get it line up with the path off the BULLET and lock down on sturdy base and I get consistent readings. Give them a call, very helpful.
That's what I did while at the range. They were extremely nice, and very helpful. Got mine up and running using 5.56, 6.5, and .308 diameter bullets. The straw trick is "on target" so to speak. It makes alignment of the unit a breeze. i haven't used it with handguns yet.