Thought some of you might find this interesting. I've had this idea for a while, for a wildcat 416 Rigby x 2.35" to stuff into a M70 short action, with a COL of 3.1", a mini-elephant gun of sorts.
And as it turns out (assume I have my math right) if you want to keep the same bolt thrust as the original Rigby, which is right about the same as the 300 RUM, you gain more speed by going with a Jeffery/RUM case in the otherwise same dimensions, simply because of the increase in MOP.
Basically, the thrust from the Rigby case at about 52.5 kpsi equals that of the RUM case at 62 k, and the 300 RUm has been chambered in the M70, so let's start there. The Jeffery, even a hair higher, almost 64k - not that you would load it there, of course, simply that bolt thrust is that much less of an issue.
That translates into the difference between a 400g @ 2340 (Rigby) and one at 2475 (RUM). [I realize those are pretty generous figures, but they're what Powley and I came up with, based on a MINIMALLY tapered case of .005/", a .35" neck and 40* shoulder. 83g/4350 and 81.5/414, resp.]
I still say the Rigby round is cooler, and it will certainly do anything the Taylor will do, "plus" perhaps, and it's always nice to keep those pressures down. Plus, I can't shake the image of a little M70 with quarter rib, three leafs, crossbolts, etc., etc.
But it was interesting to note the tradeoffs.

I find it hard to believe a ~2.0" length 404 case necked to .416" will be capable of 400 gr @ 2475. You're looking at 416 Taylor case capacity, so IMHO, would be looking more at 2300-2350 fps.

I do follow the bolt thrust thinking, though I haven't run the math. I'd also say I wouldn't need to do the math to know the light weight advantage of a short action is mute when you're driving 400 gr @ 2400 fps. Make it tip the scales at 9 pounds, and then everything is alright.

Well, Paul, first off, I'm a little dubious myself. But understand, I'm talking about 2.35", not 2", and I'm talking about the RUM, not the Jeffery. There is only a slight difference between the two, but the Jeffery is about .008" smaller at the base.
Take a look at the 416 Howell, the Jeffery x 2.5"; this little guy will beat 2475 with more modest pressures than I'm quoting, and with about twice the taper than I'm talking about as well, and on a case that's .008" smaller at the base and only .15" longer.
I won't say I know, but I'll say I think it would do it. And the Jeffery would come close.
As to the "utility" of a short-action stopper, well....
Anyway, weight-wise, put a 24" #6 on and you're getting into the high-8's. If not 9# all-up. If you have in mind a 9# rifle, it's alot easier to make it weigh more than less.
The biggest problem with the Rigby case is feeding. If I knew someone that would make a M70 short feed three of these from the mag, it would make my wallet tremble. Just figure a way to get the word "Short" on the case head and you have headstamped brass. ;-)

Why not!! Mr. Ke Waters built his 416 Express on a necked up 350 RM case and it worked out pretty good. Yours should do a lot more.

Aloha, Mark

Lazzeroni has a 2.1" .416 off of the rigby case and it does 2450 fps with a 400 gr bullet. For mono solids, you could load them a bit long and still be in the right area. If you lengthen to 2.3, you could hold the velocity while lowering the pressure a bit.
As for a M-70, have a smith take a short action and set it up with a detachable single stack clip.
As mentioned above, the short action advantage would be speed of cycling the action, although you could make a dandy light stopping rifle with it. Equip it with a brake for range time and take it off for hunting.

Definitely a potent round, but his actions have a bit more lug bearing than the M70. That allows him to load it to 64k or whatever. Too hot for my comfort, on a Mauser-style anyway.
And the shoulder starts at about 1.7" or a bit shorter. That means a 3.1" load would need at least 1.4" long. That's a big bullet. But one could use the longer case, and place the shoulder forward, like my short Rigby design, but that's not gaining you anything except a little smaller rim and even more expensive cases. I like the idea of getting the word "Short" stamped on some Rigby's. That would be a hoot.
The detach mag is an interesting proposition. Haven't considered it. I hear it takes a bit of devil's magic to get those to feed right, aftermarket.
Wonder what the rail dims would need to be, to feed off a staggered mag.

Your short Rigby would probably need to end up at 3.2" OAL to feed from a staggered mag, for controlled feed that is. At that, you might as well use the new .404 Dakota, it is based off of the rigby at, I beleive, a 2.5" case.
For a detachable magazine, the magazine could have the rails integral to it. Easier to tweak the mags instead of the action.
Here is another idea if you can tolerate 3 rounds down and one in the tube, use a .505 Gibbs case (.635" base) shortened to 2.2" with an OAL of 2.8" to 3.0". Either a .416" or .458" would be good. A .500 AHR or Jeffrey case (.620" base) could work as well. Always lots of ideas but never enough time or money to try them all.

quote:

---

Originally posted by DaveC:
Your short Rigby would probably need to end up at 3.2" OAL to feed from a staggered mag, for controlled feed that is.

---

Please explain. I'd love to know all there is to know about feed timing, and really know next to nothing. But I don't see how .1" would make or break a feeding issue. Seems a lot would have to do with how tapered the case is.
The round is pushed against the side, against one rail, and due to taper (and the the relationship of the round to center as it pushes against the round beneath it) must be pushed forward via rim against bolt until the round comes close enough to center that it slips up under the extractor. The WSM is 90% as long as this round, and 94% as fat, so it seems that the length-to-width ratio is on my side, if that means anything.
I admit it's very hard for me to think in 4-D like this. Too much beer, methinks.

Well, the fatter the case, the longer the OAL needs to be so it will feed reliably from a staggered mag (when using a CRF action). With a wider rim/case the angle may be too much for the claw to grab the rim in a short action. It all depends on the angle and the gap. You don't want too much gap in the claw either. With a push feed, there is no issue. A single stack magazine would be much easier to feed a short fat round in a CRF action.
The down side to going to a short action with a fat case is you reduce magazine capacity, especially if a single stack mag is used, unless the mag would protude below the stock as on some of the CZ's.

As DaveC has said you get a single stack made and it won't need to stick down much to hold 3. Wby do 3 with their drop magazine and remember the 378 case is Rigby size plus the extra belt.

If you try and visualise vertical stack but lating the cartridges against each other you get the wrong idea of capacity. The reason is that they are more or less staggered in the box but funnel up through lips. If can get a look at any of the Weatherbys in a shop from 30/378 through to 460 you will get the idea.

As DaveC also says, those short fat cartridges are not ideal for staggered feed on the CRF.

I would not worry about bolt thrust. In fact some of the people on this forum who make the most noise about bolt thrust are the very same people that say Weatherbys only have 3 or 4 lugs bearing. You would reckon after all those hot 30/378 and 378 loads all 9 lugs would be bearing

I think the main issue would be if you are going to cut those 416 Rigbys way back then your new neck will need some thinning as it will be formed by the body of the Rigby case.

Mike

The bolt thrust has nothing whatever to do with case body taper or base diameter. It is determied by the pressure-time relationship of the internal ballistics and the resulting force on the bullet (and correspondingly on the rifle). The nearest corrolary to bolt thrust is recoil. More recoil, more bolt thrust.

Consider: if bolt thrust were dictated by case head diameter and operating pressure, then a .257 Weatherby and a .458 Lott would have the same bolt thrust. Do you believe that? How could the shooter be slammed harder than the bolt lugs and breechface? I don't know who first came up with this idea that its peak chamber pressure multiplied by base area, but that is a gross misapplication of fluid mechanics to a problem where it doesn't apply.

So, neglecting all of that, I'd say the concept was interesting, though personally I would opt for the Jeffery case. The Rigby is massive. Good luck trying to neck that brass at that length!

257 WEA has more peak bolt thrust than Lott, as
quantified by peak pressure times the area of the inside of the case base. It has higher peak pressure on the same size base.Peak bolt thrust is the determining factor in safety and gun design....Recoil is based on the rifle weight accelerated to certain speed in reaction to what wt of bullet it has to push, and the speed it pushes bullet at, determined by powder wt,type,bore, chamber shape, etc; and the rifle weight.Copper crusher tests confirm the
case base times peak pressure as thet
relate to the amounts of peak bolt thrust.All gun designers use the peak bolt thrust
variable to make their rifle safe with about 3
multiples of safety built in to handle peak bolt thrust.Bigger the case, heavier the gun is built in the bolt and lug areas, to give the safety margin needed.

As far as Bwanas project if his case was only
an inch long to the shoulder, the sides of the case on firing would expand and grip sides to
hold more thrust than what it takes to stretch the case against the tensile strength
of the brass case sides. So 50k psi in a case
will put out same peak bolt thrust whether case is 1 inch or 3 inches long.Or pushing bullet
same diameter as case inside(Lott) or pushing bullet half the size of case inside(257WEA),
Ed