speeds variations

[clawman]

Why do loads vary through my chrono?
Rifle - Benelli A5
caliber - 338 win mag
1st shot 2772
2nd shot 2961
3rd shot 2750.
Shot placement does not necessarily correspond with pressure variances an the cases o not reflect 190 fps variance.
How much should I trust my Pact chrono?

 

[dok7mm]

You didn't state whether you are shooting factory ammo or reloads. Possible causes are : faulty chrono, imprecise set-up of chrono, neck tension variance, actual powder charge variance, age of ammo and storage history, consistent base to ogive length and I could go on and on. Finally, a 3 shot group is a poor measurement of how consistent a load is. If you shot a quick 3 rounds over a chronograph, most likely the barrel heat is the culprit --- or you left an unfired round in a heated chamber a little longer before getting your shot off. Hope this gives you some things to check.