So, if the Marlin can handle the 450 Alaskan, Why not make a wildcat on the Rigby case, 2.105" long, .560" at the shoulder, etc., etc, for about 99g of water?
Seems it would be a thumper in that 26" bbl Cowboy. Wonder what a 510g FN would do at 40k psi? 2150fps? The Lott has about 106g, for comparison.
Anyone ever seen anything like it?
I've felt the 45-70 in that gun, at full loads, and it's plenty for the shoulder as-is. And if I had one myself, I'd prolly not mess with it. Or would I....?

Bb, not sure if I'd expect any big gain with that over the .45-70 or not. Have some first and second hand experience with the 1895 CB shooting 510gr Paper Patch(MOA) and it will cruise 1600 fps with something around the low 30 gr charge level of Rx7. If load data is to be believed, 1800 fps or higher is attainable with reasonable charges, maybe pushing the pressure limits a hair. I found recoil to be strong but not uncomfortable when standing on my hind feet, but not something to relish over the sandbags. Still, I suspect it would be managable at top load levels. Penetration is what you want, depending on alloy/hardness. Ample is hardly descriptive...even with 1:20.

The '95 CB transmits recoil in a more friendly manner than I anticipated, however it is still a levergun and has attendent issues in that regard. Somewhere up the "thump index" it's going to get ugly.

To get to the point, I think it's a thumper already but grant you may gain some advantage with the Rigby Cat. Question I have though, how dead is dead?

You are probably in the ballpark with that velocity. Maybe a bit more if you put it in a bolt action rifle. It will let you know when it goes off but not too much recoil to handle. That is a good looking wildcat. Keep us posted on development.

Your wildcat sounds like the 50 Alaskan, in practice. I get 2600fps with a 300 grain woodleigh and 1850 fps with the 535 grain woodleigh out of my 26" 1895 cowboy at 32,000 cup. The modifications were fairly easy because of the similar rim size between the 45/70 and the 348 case. I have no idea what type of feeding and action issues would be involved with a rigby case.

Well, the rim on the 348 and 45-70 are about .610" and the Rigby is about .590", so that shouldn't be an issue at all.

Oh, and Dan, about how dead is dead, are you suggesting there's no place for a cartridge that pushes .458" bullets faster than the 45-70 does? After all, a 30-30 will kill a grizz sometimes.

I've been wondering about the RUM or WSM case. I ordered an extra 375 win barrel for my mod 94 Big Bore. What about a 375 WSM? or 405 WSM?
The Rigby case would have more capacity, but the WSM cases are cheaper.
Does it need to have a rim for proper functioning?
Maybe get the 50-110 cases from Starline as a starting point?

Well, there shouldn't be any problem with the rimless, since there's a number of rimless cartridges around in lever actions. The WSM case is basically the 50-110 shortened and rim turned down, and that's also what the 348 was made from, and therefor the Alaskans as well.
So, what you'll be getting are rimless Alaskans with cheaper brass, perhaps.
And since the Malrin will only handle a cartridge around 3.6" COL (or a little less) there's no reason to use the 50-110 cases.
If you wonder about the ballistics, just figure a WSM at <40k psi. I'm sure it would work well, but I don't think there will be much more speed than the 45-70, or its wildcats. Don't know offhand,m but aren't the 375 Barnes and 400 Barnes on the 45-70 case? Might be worth looking at.
The cost of cases is pretty negligable in the long run, since doing this sort of thing is never about moneywisdom anyway. Break down and buy 20 cases, then another 20 for your next couple Xmas presents and you're good for life.

And I hear they do some pretty extensive mods to the rifle to get it to shoot heavy Alaskan loads, so if that's truly necessary it may be really expensive. Then again, that may have just been for the '71. The new Marlins are pretty strong.

Who can get a Marlin to cycle a 3.6" round? I believe 2.8" is pushing it with quite a bit of work by a good gunsmith.

Typo.
Make that "2.60."
The 45-70 is 2.550" long. I'm, thinking this round would require no mods other than cutting the chamber. The rim is .018" wider on the 45-70, but turning the barrel back .005-7" would cure that with no real detriment to the inletting. Even if you did have to put a new extractor on, that's really nothing.
Gun: $550
Reamer $150
Chamber $40
Dies $100
So, maybe like $800, though you'd want a $30 Pachmayr on it after all that. Certainly much less than having the Alaskan conversion done, especially if you want the original 2.8" round. And even with the difference in COL's I think this round would give about 13% more room under a bullet. That's akin to the difference between the 458 Win and the Lott round.

And BTW, I drew up a .358" version, and it really has me thinking. It would require a new barrel, unlike the .458" round, but anything near 95g water capacity would produce some serious oomph behind a 35-cal bullet.
The 358 STA has about 100g, and though it's loaded to a much higher pressure, might give you an idea of what a good 250g FN might do out of a 26" bbl. It would certainly go a long way toward mitigating the lower BC's associated with tube mags.

Bwana-Be
There was/is a fella lived up at Lonesome Lk. near Bella Coola, B.C. by the name of Turner.
All he ever carried was a 30-30 Mod 94 he sent a few grizzlys to the happy huntin grounds with that rifle but I think most of his shooting was point blank!

ZOINKS!
Not my idea of a good time! More pow(d)er to him!

Bb, no I was not saying that. I do question the utility of a .458 Win equivalent load in a CB Gun. Not knowing what field of battle you have in mind leaves me somewhat at a disadvantage. I'm unaware of any animal in North America that will stand up to a proper load from a 45-70, and they shoot 510 gr bullets fine, giving you an advantage in SD and BC as compared to a .50 cal. Given same form, weight and hardness the .45 bore will penetrate somewhat better. I've not been persuaded that trading off weight for velocity is always a good thing in any case, and I think the .50 would carry a bit more weight with advantage. 500 grains is homeplate for the .45 bore IMO. All that said, do it if you like, I wouldn't. You seemed to be seeking opinions, that's mine.

Yeah, Dan, I have to agree with you on the effectiveness of the 45-70. And as mentioned, that 1895 CB really pounds you at the bench.
I'm certainly not planning any hunts that would require more power, but there's a certain charm in duplicating the 470 NE. This 'cat will fall short of that by some 500 ft lb, but I still like the idea. In fact, I've been enamoured of the 450 Alaskan, and this thing would top it by my guesses.
It's all fun and games for me anyway.

Wasn't the 450 Alaskan built on the Win. 1886/M71 frames? A much heavier rifle than the Marlin 1895. The major draw backs to heavy loads in this model is the lack of weight, the small size of the butt plate to spread out the recoil and the Marlins action is to short to properly seat a 500gr bullet in the 45-70. Either, the extra heavy cartiridge chambering goes into the Win.1886/M71 frame. Or restocking the Marlin and using a much heavier barrel, to get the weight up, and staying with in the limits of the actions OAL limits.

I love my Marlins, I have seven of them, most for at least 35 years. They will always have a home with me. But they do have there design limits.

Last spring I talked with two Marlin reps at a shoot about their rifles not weighing enough to soak up heavy recoil. I have a limited edition 45-70 carbine, that I have tried hotter loads in and I was glad to finally get them shot up. There is not much over 8-10 oz weight difference between it and the 26" CB. It is a shame that whem Marlin came out with the new "1895" that they used a modified 336, instead of the full lenght original 1895. The old one was chambered in 45-90 and othern longer rounds.

JM 2 cents.

Hog killer

Yup. The ywould've done a great service if they'd gone through the trouble of tooling up for a real repro. Not sure what a 50-110 would do at 40k psi, but I bet it would be fun.
As for weight, well, it's alot easier to make it weigh more than less.
To me that's one of the joys of the CB model: you have that exceptionally long barrel with really no loss of totability. All it really needs is a good Pachmayr or similar on the butt and it's much more enjoyable to shoot. And one needn't hammer off twenty rounds of heaviest loads at any one time.
I once shot a "45-70" load of 510g at about 1850, from a single-shot that allowed a COL of about 2.8" and it wasn't something I wanted four of. But three, offhand, were a few tons of fun (about 6 tons, I guess.) That rifle weighed a bit less than the CB IIRC.
Tell you what I think's nuts, these guys hot-rodding the little Guide Gun. That thing can't weigh anything. But I'm sure it's a blast.

With the muzzle brake I'm certain it is a blast.