Chronograph accuracy

[berettaprofessor]

I always bring a 22lr along for a sanity check.

The most practical advice I've seen in quite a long while.....

 

[Unclenick]

Yes. I think Dr. Ken Oehler uses a BB gun as a check, too, but I've forgotten the reason for that choice. The 22 LR in a rifle barrel is a good choice because the powder all burns up inside any barrel of about 18" or longer, and the expansion ratio is so large, individual chamber differences have little effect. Past about 18 inches, bullet velocity changes very little. Even at 24" velocity is about the same. So if you use match ammo, it will generally achieve the number stated on the box within 50 fps.

 

[hounddawg]

two rounds over the chrony were pretty much spot on. Next up was my 222 Remington which was the rifle I had really goofy results with before. The first few rounds were looking like they were in the ball park. Then velocities displayed jumped about 100 fps, and became more erratic. So, a deer rifle (243) was next. First two rounds the velocities were similar to several different range sessions a few months ago. Then sure enough, displayed velocities went higher every round for 5 rounds.

Something does no add up here. You do not mention turning the chrono off when you switch rifles and say the first few rounds from each rifle were what you expected. Seems to me though is if it were the electronics warming up causing abnormal readings the second and third rifles would display abnormal readings from the first shot.

 

[Colorado Redneck]

Hounddawg....I know. Baffling.
I was suspicious that the 222 wasn't getting complete powder burn so took the chrony out 25 ft. That isn't the issue. However, the problem no longer exists.