My go-to load is 46gr.IMR-4831, either 130 Berger VLD Hunter or 129 Hornady SP Interlock, RWS LR primers (yeah, I have a serious stash of them), and Lapua brass. OAL is longer than spec'ed because the Ruger 1A has a really deep throat. Accuracy is pretty decent- 1/2 to 3/4 MOA for three shoots, rarely over 1 MOA for five shots.
I kept coming back to IMR-4831 with my Swedish Mausers that came and went over the years, and now the Ruger 1A seems to dote on it. Frankly, I can't try every suitable powder known to mankind and IMR-4831 returns consistent performance so I stopped there - with plenty of other irons in the fire, I have enough experimenting to do to last me.
