Redpep,
Thats a good rule to follow. In my case I've had the gun for 5 years and bought it new. It is sighted in and I shot at least a dozen shots through the chrono with no issues. The last shot, for some reason, the sabot took a nose dive as it passed over the chrono and hit in the center of the far plastic cover that holds the sensor. If it had been the front of the chrono and had the display built in it would have been in the center of the display. How it hit in that place on the rear sensor I can't explain but it had a small piece of plastic the same color as the sabot. I'm going to fashion some kind of cover to protect the internal area before I use it again.

Cascadedad,
The .501/.503 was in reference to my earlier post about the labeling on the 2 boxes of Bull Shop 460's and the possibility that they were reversed in their labeling.

Dave,
I resisted getting a chrono for a long time but now find it an invaluable tool for verifying loads and developing data about those loads. I use to do it the old fashion way of shooting at various ranges and seeing what the load can do, I still do that but having the added level of confidence in the velocity and its consistancy is a nice bonus. With all the shooting and testing you do it would benifit many on this forum in addition to you if you got one.