powder for a .284 with long barrel
My gunsmith is finishing a prone rifle for me in .284 with a Bartlein 30 inch, 1 in 9 twist barrel. This weapon is meant for shooting with a bipod and the 160-180 grain bullets are better in dealing with the winds that blow off the high Rockies here. In testing before completion we find that Alliant RE17 shoots the exact same velocity in the 30 inch barrel as it does with a 25 inch barrel using the Hornady Amax bullets.
I am hoping someone using this website has practical knowledge as to which powder gets the maximum utilization of this long barrel, using the 160-180 grain 7mm bullets?