The Hornet barrel has never been factory offered on an SB1 frame, although it has been offered on older(pre-'87) H&R Inc Topper cast iron frames and may work fine on an SB1 frame as long as the right primers are used. I've had severely cratered primers on one shotgun frame and lightly cratered primers on another even using Lil'gun in the hornet which operates at less pressure than other hornet powders, some of those that use other powders have reported pierced primers, so beware.
The Versa Pack came on an SB1 frame, H&R would not fit any other barrels to it, this is discussed at length in the H&R Rimfire forum sticky IIRC.
Tim