manodiablo...welcome to the insanity club

500 rigby sounds good but it is on mbogo brass so 500 mbogo is more correct but if it is your gun you get to name it. 500 rigby-mbogo???

thank you gentlemen, especially Manodiablo for the posts. So much food for thought. I have a 458 Lott and want a (preferably) 50 before stepping up to a 550RNS (the holy grail). I had a Krieghoff 500 NE 3" and found the recoil smooth and hardly objectionable, even a few 8-10 round bouts from the bench. I want to replicate that power, or a bit more, with a boltgun. I am guessing that cast bullet loads in the 550RNS might be the answer, but I would like a 500 on this Remington model of 1934 action I have acquired; and was wanting to skip the belted hassle.

We shall see....

thanks again,

Rich

Gentlemen:

My apologies to all. The rambling reply to Idaho Sharps- was meant to be a PM.

I am now found out to be big bore bolt banana (damn).

(I also play with two 10.75x68s, one an Oberndorf sporter and one I had made, as I could not bear to scope drill the Oberndorf, as a measure of my sanity. Greased bar chin-ups...)

However, I have learned here that the headspacing on the 10.75 Mauser, with which I
have been comfortable for years, is LESS than the proposed .500 Rigby, so damn it I am going to do it.

After this rant I actually visited several shops...the estimate on the CZ550/602 is sharply up.
Used 602s have tripled in price due, I assume, to the Hollywood finish on the big 550.

what is with that CAVERNOUS hole in the 550 magnum stock for the bolt handle? You could store ammo in it.

And I am insulted by the crass upscale marketing strategy of CZ-USA. One now has to pay $3K+++
to get a barrel band mounted sling swivel, whereas it was stock on the 602/early 550 for so long. Barrel band manf./install cannot be more than $5 production cost; hell of a lot cheaper than that rear sight assembly, which they did not touch. (I have some familiarity with production cost projections)
Now its $2500+ base price PLUS $200 for the band. No option on the standard rifles.

I can just imagine some advertizing type chuckling at all us poor souls laying awake
at night grinding over whether to pay a 200+%premium for a key Africana element of the big bore rifle.
(The bonus he must have earned...save money, delete production item, and simultaneously make the safari custom more desirable)

And us justifying it to get past the deliberately glitzy finish on the standard 550.

Damn all marketeers.

Sirs:

Whats wrong with me. Too focussed on the technical.

I want to thank you all for the EXPERIENCED constructive criticism, especially RIP, also Robgunbuilder, Boom Stick, Idaho Sharps-

Excellent analysis of my ramblings. One always overlooks details when thinking alone. Thinking like that leads to disasters. You folks make an effective engineering design review team.

* * *

Back to the technical (what do you expect from an engineer?)

The shoulder diameter/headspacing issues that RIP brings up indicate good safety engineering;
eliminate possibility of cross chambering either the .416 or the .450 Rigby in their respective rifles.
This also includes bullet/neck diameters of the smaller cartridge in the bigger chamber.
After all, anyone who possess a .500 Rigy probably will also possess a .416. .450, AND .350 and certainly
a .275 Rigby. So when the .500 Rigby owner shows up to the local Big Bore shoot, he is likely to be
accompanied by the very rifles which could potentially partially chamber other Rigby rounds.

(Lets see, Determined Dan fingers a lightly loaded .500 Rigby round at a Big Bore shoot (he is half qualified)
stupidly (how else) slams home a .450 Rigby bolt on it, drives the slug far enough back to crush the neck and chamber the round. Blows his hand off and you are paying the rest of your years for his stubborn stupidity. Need to add shoulder stopping to help protect him)

So the .500 Rigby should have shoulder set lower by at least 10 mils. although its larger neck/bullet
diameter should prevent live cartridge entry into its sister chambers.

Make it 2.150 for simplicity. And at 3 mils/inch taper, round up to 7 mils taper/side. Shoulder dia. is hence .590-0.014 = 0.576 inches.

The MAST brass I have measures 15 mils on the neck, just as Idaho Sharps- says.
We are playing with minimums here, need to minimize this in a controlled but adequate fashion.

Could neck turn brass to 12 mils (RIP, howzabout 10 mils?). Neck dia. then is .510 + 2(0.012)= 0.534

That leaves 0.576-0.534 = 32 mils, or 16 mils per shoulder side.

HOWEVER, this assumes ZERO tolerances everywhere. I say NO to ZERO TOLERANCE (in design and in politics).

The Neck will require say, 4 mils expansion, to release the projectile upon obturation. This reduces the shoulder support by 2 mils (from 16 down to 14 mils support per side)

While this is a wildcat, despite precise fitting/fireforming of cases, a cold day or warm cartridges could cause differential metal expansion preventing cartridge chambering, never mind dust in the air. Need more tolerance (space)!

So if we allow just 1 mil ( +0.5, -0.0)/side case wall tolerance, have to either open up the chamber or squish down the case sides Either one reduces headspace support by another 1 mils/ side. So cartridge shoulder support is now down from 14 mils/side to 13 mils/side.

Now according to RIP, my 10.75s have only 27 mils/2 = 13.5 mils support/side. Probably less in practice.
SO IT IS DOABLE, BUT JUST BARELY. Cant do it with 15 mil thick case necks, it is that close.

This cartridge requires machining precision way beyond what I could do, probably beyond what most gunsmiths can do, but not beyond a master machinist (on an aerospace basis this is straightforward, but lets get real).
(prototype machinists here have taught me that much; that the training, experience, and talent to become a master machinist easily exceeds the time to become a PhD in the sciences)

We havent mentioned axial alignment of the chambering, or centering the bolt face/assembly with its required tolerances on such a precision chamber. The entire barrel/chamber/bolt face/bolt lugs/lug recesses should be centered and trued to 1 mil OVERALL tolerance. This could be done by a master machinist, but probably not on
a production basis.

So part of the effort to build the .500 Rigby is to find a master machinist who could realistic be expected
to perform at this precision level. The reamers could be built to this precision, but employing them should
only be done by a master craftsman. Forget reboring/rechambering, that would only work by dumb luck.

Any takers?

Ciao

Mano

my dad is an r+d machinest and has done work on the space shuttle, satelites, jets, missles ect but unfortunately has no gunsmithing experience...maybe in his retirement he should take a gunsmithing course