Hmmm. reset your length to take it down another .003 and check diameter of your crimp at the mouth. I run .471. Lotta different factors involved here. Also. velocities run faster than Published in my barrel, it's a little fast. However, the books all show 5.3 grains running around 854fps or so. I'm running a tenth of a grain less and getting 835fps, you should be seeing more than 775fps.
How far away are you setting up the Chrono? Are you shooting through the upper third?
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