Re: rifle setup
Just ice your ammo and take a cold bore shot over a chrono. This will get you awful close. The elevation will not change your muzzle velocity, just the temperature. Let your rifle cool for 30 minutes then take another shot with the iced ammo. As was said earlier, you'll probably get 30-50fps less.
I hunt with a 338Allen Magnum and use 3270fps as my velocity, the JBM Litz data for the 300smk works VERY well for my drops up to and past 1200yds.
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