Digressing from the powder questions. And raising the spectre of multiple variables impacting accuracy.
The back of the rib should clear the front of the receiver by, IIRC, at least .003". Otherwise the end of the rib might contact the receiver as the barrel warms up with adverse impact on group size.
My 7 x 57 1A would shoot vertical strings with little lateral dispersion despite waiting 5 minutes or more between shots. The first shot the next day would be spot on with the first shot of the previous day! There was no clearance between the back of the rib and the receiver. I pulled the rib and stoned the back end to provide some clearance. If you elect to do this, be careful removing the flat head allen screws attaching the rib to the barrel. Penetrating oil and some heat would be your friends. I broke one of those screws....Ruger was good about sending a replacement but getting the broken stub out without buggering up the barrel was tricky. Providing rib clearance fixed the vertical stringing.
Also, older 7 x 57 Ruger 1A rifles had longer throats to handle 175 gr bullets. My 1A shoots 140 gr Nosler BTs better when the bullets are seated out further.
Finally, when was your No. 1 made? The very early ones had excellent Douglas barrels but Ruger used Wilson barrels for a while and accuracy varied with those. Ruger hammer forged barrels starting in ?1992 are supposed to be better than the Wilson barrels.
