Kenster, I think you will have good success, 4198 is never a bad choice. One of my recipes is 28 gr 4198 in Win cases, WLR primer, 1 gr dacron.
405 gr Lee Bullet is around Bhn 10-11, wheelweight + enough tin to get full fillout, Lee liquid alox. In a Trapdoor Cadet I'm getting around 1350 fps. (kinda sorta shoots to the Buffington sight) My groove diameter is about .461 ish. Now maybe, just maybe, the dacron, besides positioning the powder against the primer also protects the base of the bullet from the flame...no leading in hundreds of rounds fired. I am clanging steel to 500 yds (when the wind gods aren't making jest of me.) I would guess you have a true .458 groove in the #3 and better yet probably a perfect ball seat tapered throat, I'd bet total success.
