Standard Rigby load (400gr @ 2400fps) fired from a CZ has about 63ft/lb of recoil and it's a fairly slow roll recoil (had one of these, traded it to a guy that wanted more recoil than his 375H&H had). The standard 375H&H load (300gr @ 2550) from the same gun runs about 45ft/lb and again is a slow roll (I've fired a Amish friends 375H&H, he used it as a "stopper" when he was guiding bear hunts in AK, but haven't had the oppertunity to fire mine yet).
I find that when I exceeded 2450 with the Rigby the recoil got downright nasty. Considering that the Wby is nothing but a belted Rigby case (running 20,000psi higher pressures) it's no suprise that you can get Wby proformance out of the old girl. On the down side is that Wby's are known to cause bullets to overexpand due to higher velocities than they were designed for.
Accuracy under pressure is what counts, and odds are you will have a PH along who will be carrying one of the big thumpers JIC (that's part of his job, keeping you from getting killed/injured), so go with the one your most accurate/comfortable with.
Good luck and good hunting
My thinking on a big bore rifle is that something around a 450 Rigby would be about right. If medium fast powders could be used to get around 2450 fps with a 500 grain bullet, the barrel could possibly be as short as 20" so a muzle brake could be fitted to give an over all lenght of 22". I'm not sure this is feasible and I'm hoping someone with experience in this area will comment on this.
I've seen a Grizzly about 600 lbs shot through the heart lung area run 250' up a hill and die a couple minutes later just over the crest of the hill. And heard from a very reliable friend who shot a Griz many years ago with a 250 gr Nosler through the lungs and have it run into the bush and not die for more than an hour. These bears were in the 6-7 hundred lb range and we see pictures from time to time of bears with a live weight of 1500 lbs. If I ever get the 03:00 call from Mr Horriblis, I want the most powerful gun I can reasonably handle. A short barrel and weight no more than 12 lbs to be able to use it in short quarters.
Been hunting in Africa a few times back in the 80's and 90's hunting a mix of plains and dangerous game. My two favorites for the type of hunting I did was a Whitworth H&H 375 and a 450 H&H Dominion Double Express. In also own and shot 458WM, Wetherby, and the 416 Rigby. I think the choice of caliber depends largely on the nature and circumstances of the hunt. For the non dangerous antelope, warthog, zebra, etc and leopards, lions over bait, the 375 worked perfectly. The beauty of this caliber is that with minimal trigger time it will handle and feel like your pet 30-06 with little difference in felt recoil. All the game mentioned dropped like they were electrocuted with perfect bullet performance using run of the mill Winchester 270 gr power points. POI was identical using 300gr solids for buffalo. Trajectories with a 270gr were identical to a 180 gr 30-06. This rifle is a good choice for the North American big bears. For cape buffalo and tracking lions in thick cover, while every thing can go smoothly with a 375, if it doesn't, it's TOO small and a 458 cal or larger with a 500 grain bullet is minimum. For Lion I like a soft point and for Buffalo, a solid. At 20 yards, the possibility of not having a PH backing you up(two times for me), accuracy, speed, and damage is critical. With their steam up, you can't shock a cape buffalo with velocity, penetration/damage is critical. My 450 H&H sending a 480 gr solid at 2150FPS will send an expanded bullet lengthwise through a Lion, chest to azzhole, and a solid clear through a buffalo broad side breaking bone. While I really like my Rigby, I think that as a general purpose rifle it's caught in the middle, too big for the antelope species, and somewhat small for a disturbed buffalo. While bullet technology may have changed since I hunted Africa, most of the PH's seemed to frown on the ultra high velocity big bores believing it hindered straight line penetration, enhanced bullet fragmentation hitting the heavy bone of a buffalo, and were difficult to control unless the shooter was well practiced under pressure. For plains game they felt the high velocity loads did unnecessary meat damage. They fed the camp with this game. I'm sure there are many views on this subject and in no way declare them as gospel. Just thought I would share my experience.
"Let us speak courteously, deal fairly, and keep ourselves armed and ready"-T. Roosevelt
Like everyone else I have an OPINION to. (And that's what it is) you are going to get many recommendations and all will do the job.
My choice, was based on an all round cartridge that could be Manageable, would stop anything,
have good trajectory, (For plains game) good bullet selection,(Weight and construction) .
I would chose a 416 caliber. the type of 416 would be a personal choice. I have shot most of the big bores and found good and bad in all of them. the first serous big bore I bought was a 416 Rem Mag
because it was about the same as the Rigby but easier to buy a rifle and ammo for. I found the downside pretty fast, The 416 RM is very heat sensitive and in Temp.s over 100o they become to hot and extraction can be an issue.
I am a big fan of the Weatherby, but if you shoot one you will find its short comings also (Recoil and cost)
So not being able to leave well enough alone I tried to combine all the up side and eliminate the down side.
Performance and cost led me to the 375 RUM case necked up to 416. This round could be used in a standard Mag Bolt face Remington or any other action (Cost), The 375/416 RUM wildcat boosted the velocity 200+ ft/sec over the 416 RM without any pressure signs, eliminating temp sensitive ammo
and good brass that does not cost an arm and a leg.
Recoil is brisk (As on any big bore) but not as much as the 416 Weatherby or most of the .458s
This would be considered by me to be an all round big game rifle good for anything in the world
without giving up any thing.
There are many good choices for dangerous game starting around the 375 H&H and going up to
a 50 BMG but somewhere you have to chose the best for you, the game and what is enough for
the task at hand.
This poll, although interesting, is nearly ten years old. I would like to see a poll of LRH members to find out which "big bore" (though I believe everything up to .416 is technically classified as a medium bore) chambered rifles they own.
I think it would be interesting to see how many people own such rifles in the entry level cartridges like .416 Remington, .416 Ruger, .375 Ruger and H&H, how many people have stepped up to the RUM, Rigby, .378 Weatherby class cartridges, and how many have gone all out and stepped up to the Barrett, Cheytac, and Allen Magnum cartridges.