Unfortunately the same load won't always give the same velocity in 2 different pistols, even with the same barrel length. If you have access to a chrono (and it sounds like you do) then try bumping the charge up 0.2 grains and see if that makes it. One of my manuals says it will take 5.9 to make 850 even with a 5" barrel.
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No Second Place Winner
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No Second Place Winner