My post '64 Model 70 has a 24" barrel with 1:12 twist. Works fine with bullets from 200 gn up to the 310 gn Woodleigh. It is not fussy about powder but I prefer Varget for 255 gn bullets and H4350 for heavier bullets. IMR4451 seems just as good as H4350 but takes 1 grain less. My favorite bullet is the Nosler 250 gn. The 250 Speer is slightly less accurate and develops a little more pressure so I use 1 gn less powder with it.
To use .338 Win Mag brass I just run it through the .358 sizer die, load with a normal powder charge and shoot. These fire forming loads are just as accurate as loads with already formed cases. You can also use .300 Win Mag brass by running it through the sizer die and trimming.
