That's a new one, the Ruger SBH not being that accurate out of the box, only NIB 44 Magnums I ever heard about having accuracy problems were some of the first production Virginian Dragoons due to oversized throats. IMHO accuracy problems with a Ruger SBH are due to uncomfortable grips and shooters who overestimate their shooting abilities.
You did not state if you were using cast or jacketed bullets. The more knowledgeable reloaders and bullet casters will emphasize the value of slugging your bore and casting bullets that fit it well, with jacketed bullets
firn the brand that works best for you. Best rule for load development is to load 5 rounds with increasing powder increments until you find your pet load.