...just back from a short trip...appreciate the responses...

...my interest in the take-down heym express has more to do with ease of travel (and cleaning) than the ability to switch barrels...and, with a .416 rigby (or perhaps .500 jefferey) and less than 150 yard shooting distances, moa is not that critical, so long as actual accuracy is within the range of reasonablness hunting-wise (e.g., 1.5-2.0 moa at 100 yards)...

...i suppose at the end of the day i really just want to rid myself of the ruger rsm and acquire a semi-quality big bore turnbolt that can somewhat emulate the ease of a take-down double...