Your question is ill-phrased. In Speer ammo, "SB" means Short Barrel and refers to a load with 135 grain JHP bullet in 38 Special and .357 Magnum ammo. It is intended to give good expansion at relatively low velocities in snub barrels.

You obviously mean something else, maybe component bullets in .429" size?

I haven't owned a .44 in years and may just be missing some new product? I guess BB is Bevel Base?

If they're now making SWC-HP ammo in .44 Magnum and .44 Special, that's important news... to me. I know they've made solid bullets like that for decades, but HP's? That'd be terrific, if they expand well. Who knows something about this?