The longer barrel length should have NO effect on your "published load data" You will probably get a little more velocity with the extra barrel length. By NO means use "More Powder", with out starting low and working up. It is possible depending on the cartridge that going to a slightly slower burning powder would get a few more FPS without increasing pressure since you have more barrel in which to burn the powder.
Stay with the minimum or "Starting loads" until you know how your rifle reacts to them, variations in chamber size, case capacity among things can result in very bad things happening if you start with a heavy or max load.
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