I believe the Rigby may be a replica of one of the .451 bored rifles which were used in the "smallbore" target matches in England in the late 1800s. I guess you could call them sort of a second generation Whitworth inasmuch as they shoot a very long slug which is under bore size by a whisker, an innovation that originated with Whitworth. The Whitworth used a fast twist to stabilize the long bullet which had to take the rifling due to the mechanical fit of bullet to bore. It was discovered that the long bullet would expand and fill the bore when a charge of 70 grains or so of powder was used. Round bullets fired in a six sided Whitworth bore became six sided bullets by the time they left the muzzle. Since the whole purpose of the six sided bore was to force an undersised bullet to spin and a long bullet was found to expand into the rifling, several new rifling configurations were tried. A standard round bore was found to work as well as the Whitworth six sided bore and the Alexander Henry rifling which was sort of a hybrid between the Whitworth and a round bore.
The Rigby, Gibbs, and the Volunteer rifles were all used in long range target matches and are still used today to shoot the 1000 yard muzzleloading rifle matches. I don't know about shooting other, shorter bullets from one, saboted or otherwise. They depend on the inertia, I think, of that really heavy bullet to resist starting to move at the moment of firing enough to expand into the rifling. A shorter, lighter bullet might not expand and just rattle down the rifling. I have some 250 grain bullets for my .45 Colt I sized to .450 which I intend to try out in my Volunteer just for grins but I haven't got around to it yet.
A by product of that long lead 550 grain slug expanding into the rifling is considerably higher pressure than with a patched round ball. The nipple on a Whitworth or one of the others like it will erode rapidly, even after as few as 25 shots I have heard. The 1000 yard guys all equip their rifles with platinum lined nipples to cope with that. I put one on my Volunteer when I got it and have had no trouble with nipple erosion after several hundred rounds.
I killed two deer with it this year and was very pleased with the performance. I think a bullet from it would penetrate completely through one, longways, and just keep on going. The meat damage was minimal. These rifles are capable of very fine accuracy,as you might guess from the 1000 yard thing, and are a good choice for one who wants a traditional rifle with capabilities normally only found in the modern in-lines.
Steve
