two of my .264s. bottom rifle here is M700/26" Brux 1:8" Rem. sporter contour/McMillan Classic ADL/6X42 M1/Jewell. it's .264 and weighs 8# 5 oz. as pictured.
don't obcess over getting every last fps. I got a pard that has a .264 Featherweight with 22" barrel and he kills stuff with it. that said, I spec my .264s with 26" barrels. I do think you'll be a little over your weight estimate with the #3.
my reamer is cut to allow 142 SMKs to kiss at 3.3"