I have used imr 4064 ever since i got a rem model 7 with the 20 inch barrel. Try starting with about 36 grains with the 120 grain sierra and top out around 38 or 39 grains. With a 100 grain bullet try starting around 38 grains and you will top out between 40 and 41 grains. These are not real hot loads but they are accurate in my model 7
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