I carried my brand new 527 CZ .223 to the range today to zero the scope and clock a few loads. I strapped the Magneto Speed on the barrel and plugged it into the display and took a small wooden dowel about 16" long and put it in the barrel to make sure a bullet wouldn't hit the unit. Walked back and took a seat, loaded a round. took the safety off and then made the little mental check if everything was ok and that's when the alarm went off. I had left the wooden dowel in the barrel! Whew, glad I made that little check. The range officer told me later in the day that he had a stainless rod to check his Magneto Speeds alignment and left it in a 6.5 Creedmoor. It banana peeled the Kreiger barrel back about 12". Mental mistakes--we humans are bound to make them.