Take a look at the firing pin of both you will see the differance. Most 17HMR will not fire as the rimfire round needs to be struck on the rim and the centerfire ...well needs to be struck in the center. Thus we have the Versa Pack bbls that are bored off center to allow center fire pins to strike the rim. For the most part all H&R bbl can be swapped. It's just a matter of whether the pressures are ok ,where the pin strikes and what kind of pin it actually is and how the frame was manufactured. Kurt