I breech seat .32-40's in ASSRA competition and pleasure shooting. I stick with the tried and true 14gr. 4227 for the tapered 185 Hudson bullet that's my favorite out of the half dozen or so moulds I have. Works a treat in my two main rifles: an original Pope barreled High Wall and an "unknown" barreled High Wall. We shall see how the two new ones I'm building on a Ballard and a HW action play out. I could muzzle-breech load the Pope but the only advantage with that system is with black powder, in that the act of muzzle loading the bullet clears the BP fouling deposited by the previous shot. Pope himself said that there's little inherent difference between muzzle loading and breech seating save for the cleansing. (That and the very slight advantage of muzzle loading pulling the burrs of displaced lead made by the lands to the top of the driving bands rather than having them project past the base as with a conventionally loaded bullet.)
4759 works equally well for me but I'm saving my last 15 pounds or so for .30 gas checked shooting. AA9 and 5744 have performed beautifully for me too but due to spotty local availability I shy away from them.
Is the chamber of your Weber breech seater made from a case fired in that chamber, with its pusher rod sized for a sweet fit also? If not, you should consider doing so. Breech seating is all about inserting the bullet straight into the rifling and that won't happen if the tool isn't a perfect fit.