Chrono variances

[Papershredder]

Rocks and I were at the range the other day and he was thinking that a load he had worked up for his .270WSM last fall should be faster than the readings he was seeing. He was already set-up and using his chrony before I got to the range, so I was just going to use his chono rather than setting mine up. I fired a round that was reading around 3425fps on my chony the day before, thru Rocks' chrono and only got about 3250fps. I figured something was not right;as the velocity I was seeing the day before was very close to what Ty at Barnes figured I should be seeing. We then set up my chrono and Rocks fired a round thru it, with his .270WSM that he thought was only around 2900fps(thru his chrono), this came up at about 3150fps thru mine,(about where it should be). Has anyone else seen this happen? Either mine is reading fast, or his is reading slow. Can a Chrony be calibrated? I believe Rocks has a Gamma Master, mine is just an F1.

[WCTHEMI]

I believe they can be calibrated, the manufacturer would have the procedure. Maybe the lights are getting weak in it?

[Rocks]

The chrony I'm using was brand new last fall, and it seemed to read slow right from the get-go. Loads were consistently 150 or 200 fps slower than what the book said they should be, and then shooting it with Shredder's the other day I'm convinced mine is out of whack.

There's nothing in the manual about calibrating, I'll have to phone the manufacturer and check it out. Otherwise if I can locate the reciept it's going back...

[Dick284]

Yup it's somewhat normal.
The only true way to tell if your chrony is accurate or not is to plot your real world trajectory against the trajectory as computed using a ballistics program.
So shoot groups to at least 300 yds, 500 is better see how it plays out to crunched numbers, and then you'll have some idea if your chrony is otl, or more or less accurate.

[Papershredder]

Thanx guys.