Brothers Gibbs:
.408 Chey-Tac
..475 Gibbs
...505 Gibbs
....510 Gibbs



470 Mbogo and .475 Gibbs:



.475/.416 Rigby Norma
..470 Mbogo from Jamison Basic
...500 Mbogo from Jamison Basic
....500 Mbogo from Jamison Basic
.....500 Mbogo from Norma .416 Rigby
......500 Mbogo from Norma .416 Rigby



CZ bolt face opened for the .640" rim of a .505 Gibbs: Ouch! That extractor edge needs some work!


The CZ magazine box is also too small in width for the .505 Gibbs.

Since anything over .510 caliber is silly, this all adds up to: 500 Mbogo

The .510 Kayser Express will also do, because the reamer that was made up for that is closer to a .510/470 Mbogo than it is to a "beltless .510 Wells."

I wonder if using .510 Wells dies to reload the .510 KE will be reliable on headspacing, as the shoulder is bound to be smaller than the 500 Mbogo's 20 thou and 35 degrees per side.

OK. Who is gonna do the 550 Gibbs Improved?

quote:

Originally posted by fla3006:
OK. Who is gonna do the 550 Gibbs Improved?

HIGHJACK!!!

Why did Geoff McDonald stop at the "505/530 Woodleigh": a .505 Gibbs necked up to throw a .530 caliber 750 grain Woodleigh bullet???

That was foolish enough, and you want more???

Remember, over .510 caliber and about 600 grains and the torque and portability/weight issues make the rifle silly.

The bigger bolt diameter and bigger box width for a .505 Gibbs based cartridge are a needless complication when you can move a 600 grainer at 2500 fps from a 500 Mbogo.

Bolt thrust issues too, with the bigger .505 Gibbs case head.

With the Rigby case head from Jamison you can load them as hot as anything, if you relish the punishment.

So is anybody going to spell out the blown out Gibbs shoulder and neck diameters to handle a .550 caliber bullet?

How many thou and how many degrees per side?

RIP, I am sure that fla3006 made that comment with tounge firmly in cheek.

Hog Killer

Hog Killer,
No offense taken.

Forrest took the bait, or is just playing straight man for me.

This thread was inspired by the 550 Gibbs idea. Forrest read my mind.

So what if you could blow the .505 Gibbs shoulder out to .620" and neck it up to an O.D. neck of .575" to handle a .550 caliber bullet, make the shoulder angle the same, or simplify it to 35 degrees per side?

Sure, it is possible, but it is dumb.

The .550 caliber on a .460 Weatherby has socially redeeming value by comparison. Not much value, but some value by comparison.

Ron, I am just funning with you. I think your 500 Mbogo makes sense, does appear to be the optimal 500, although like the theoretical 550 Gibbs I think it is far beyond what most shooters can realistically handle on any sustainable basis, myself included.

being that there is no nostalgia with the 550 bullets the best thing is to use the stronger chey-tac brass and have the 550 chey-tak...and being there is no "tac" (tactical) it should be called the 550 cheyenne....able to dispose of pesky buffalo with a pull of a trigger.

550 cheyenne! 35 degree shoulders and 20 thou body taper cal length neck and whatever is left for shoulders...

sorry rabbi

what does master po (blind old guy from "kung fu") aka jeffeosso think about this???

rabbi rip...

is it worth moving the neck back a bit to get a cal neck on the 500 mbogo???

and what does the peanut gallery think of the 500 ahr (not rebated) shoulder moved back with a cal length trimmed to the regulat 500 jeffery length able to fit in a m98...basicly a 500 jeffery with no rebate and cal length neck.

quote:

RIP: So what if you could blow the .505 Gibbs shoulder out to .620" and neck it up to an O.D. neck of .575" to handle a .550 caliber bullet, make the shoulder angle the same, or simplify it to 35 degrees per side? Sure, it is possible, but it is dumb. The .550 caliber on a .460 Weatherby has socially redeeming value by comparison. Not much value, but some value

Well, there is the 600 OK, Nyati, Tyrannosaur, etc. so I suppose anything including a 550 Gibbs is possible. But I have watched Dave, Neal, Jeffe, Rob, Harry and others at Camp Cooley and the bubba shoots with their cannons and these rounds are in a whole other realm. No thank you please. My practical limit is the Lott, Rigby and Wells light.

boom stick,
When you form the 500 Mbogo from Jamison 470 Mbogo basic cylindrical brass, you get a neck that is about 90% of caliber length, and if we let the brass grow to a 3.000" max (trim to 2.990") we get neck lengths of .505" and a trim to .495" neck length.

That is plenty of neck. I consider 90% to 100% of caliber for neck length to be perfect. Thanks to Fred Zeglin's guidelines.

The 470 Mbogo is 2.9450" long (max). The neck is only .4150" at that. This is 87.4% of caliber, but close enough to 90%. It works.

Just necking the 470 Mbogo up to .510 caliber moves the neck-shoulder juncture toward the base of the case by about .035". That adds to neck length in the 500 Mbogo.

The 500 Mbogo will be reamed for a max brass length of 3.000".

I would not want to change the 470 Mbogo shoulder as the basis of the 500 Mbogo. The juncture of case body with the start of the shoulder will not change. It will use the same headspace guage as the 470 Mbogo. It would not be a 500 Mbogo if I changed that.

quote:

Originally posted by fla3006:
[QUOTE]

Well, there is the 600 OK, Nyati, Tyrannosaur, etc. so I suppose anything including a 550 Gibbs is possible. But I have watched Dave, Neal, Jeffe, Rod, Harry and others at Camp Cooley and the bubba shoots with their cannons and these rounds are in a whole other realm. No thank you please. My practical limit is the Lott, Rigby and Wells light.

Forrest,
The 500 Mbogo is little different than the .510 Wells light.

I plan to load it with a case full of H4831SC and the long monometals (GSC HV and FN, and the Barnes TSX, all 570 grainers) to duplicate the 500 NE 3-inch.

I also plan to load it with a compressed charge of Varget to equal the hottest .510 Wells or 500 A-Square.

570 grainers at 2150 fps or 2500 fps.

What is not to like about that?

I am sure it could also equal the Ryan Breeding loads for the .505 Gibbs (which have too much bolt thrust for a CZ 550 Magnum in .505 Gibbs), or 600 grainers at 2500 fps. But that would only be for chest-thumping purposes, pun intended.

A CZ 550 Magnum can do more as a 500 Mbogo than it can do as a .505 Gibbs based wildcat. This redundantly clear when you factor in all the .510 caliber bullets and barrels available due to the 500 NE and 50 BMG, etc.

No rebate and no belt.

quote:

Originally posted by RIP:
boom stick,
When you form the 500 Mbogo from Jamison 470 Mbogo basic cylindrical brass, you get a neck that is about 90% of caliber length, and if we let the brass grow to a 3.000" max (trim to 2.990") we get neck lengths of .505" and a trim to .495" neck length.

6 of this, half dozen of the other...
That is plenty of neck. I consider 90% to 100% of caliber for neck length to be perfect. Thanks to Fred Zeglin's guidelines.

The 470 Mbogo is 2.9450" long (max). The neck is only .4150" at that. This is 87.4% of caliber, but close enough to 90%. It works.

Just necking the 470 Mbogo up to .510 caliber moves the neck-shoulder juncture toward the base of the case by about .035". That adds to neck length in the 500 Mbogo.

The 500 Mbogowill be cur with a max brass length of 3.000".

I would not want to change the 470 Mbogo shoulder as the basis of the 500 Mbogo. The juncture of case body with the start of the shoulder will not change. It will use the same headspace guage as the 470 Mbogo. It would not be a 500 Mbogo if I changed that.

if its good enough for the rabbi its good enough for me

hmmmmm....500 mbogo or 500a2 no belt...hmmmmm....

From the Peanut Gallery: I do not think the 500 AHR is meant for a standard M98, it is meant for a Rigby length box, and it has a rebated rim still, last time I looked at the specs on their web page. Rebate is less, but not by much!

the idea is basicly a 500 ahr with a shorter body that can fit in a m98...

it is not supposed to have a rebate...see the drawing

yes its not meant to fit in a m98 but it could

i preffer a mk 2 though

i still think the 500 a.r. will be ideal and better as far as practical and cheaper.

2007 will be a good year. 375 ruger and 500 a.r.

I am not, I repeat N-O-T going to tell what is going on here in the think tank regarding the future of that Remington Model 30 Express I bought one week ago tomorrow. No, no, no...NO!!

Rich

rich...550 cheyenne???

nobody will critical here...

Okay, you twisted my arm, and that ain't easy in cyberspace...
Go to the Wildcat forum and read the 550 Gibbs posts.

Rich

the 500 mbogo and 500 a.r. are like brothers

Rich,
You have more of a 500 Mbogo than a beltless .510 Wells. Admit it and get some custom dies made.

Boom stick,
From the AHR web site, Ken Howell's drawing:



19 thou of rebate.

The water capacity is stated as only 156 grains.
The brass is made by Bertram right?

rip...

the date on my drawing is 6/24/99

yours is 6/19/1999...he changed his mind and put no rebate.

rich's quotes...



Seriously,

why not a 550 Gibbs? Looking at the dimensions, that big long neck is interesting (great for cast bullets), but unecessary with a properly designed lead bullet or the available jacketed stuff.

One of you CAD geniuses can draw this up and have it posted by midnight!

The 505 Gibbs is 3.15" long, but loaded round oal is just 3.75" in length. The box on my 30 Express is 3.6" long...a Hornady 458 Lott factory load just snuggles inside atop the follower and tries to squeeze in. That means a 4" box would take 505 rounds with nearly 1/4" to spare, right? Make a single stack box and feeding problems go away?

Take the 505, which measures .640" at the base and tapers to .600" at the shoulder just 2.460" from the base to the shoulder. Shoulder angle is 38-degrees, and the neck is .660" long. No need for a neck over one caliber, and half that body taper is plenty. Blow out the body from.600" to .620", and shorten the neck .160".
Sharpen the shoulder to 45-degrees. What you lose in neck length and powder capacity, you make up by blowing the body out, give or take; so the net powder capacity remains about the same. It's a short-enough oal to make a box 3.8" long work, and that means I only have to lengthen the box .200". Mill the ends off the box and weld new ones flush with the outside of the original box, and you are there. Or, just bend up and weld a new one the right length. The only major hurdle to overcome is getting the original floor plate converted to an easy opening one.

Jeffe, you been down this road, or one very like it a hundred times. This sounds like minimal machine work to get the box length where it needs to be, and the rest should be manageable for any competent machinist/gunsmith. Would making a new box single stck size take care of feeding problems, or the Gibbs that big a pain in the ass?

Enquiring minds want to know.

Rich

This is why I love this forum and the bright lads on it! You just knew guys before Bwana-be had looked at this, although Bwana-be deserves kudos!! for actually looking at numbers and postulating them here. BTW B-b, I did not mean to hi-jack your thread; you get all the credit in my mind since you got here first. Bravo!
I just miked the 30X and that boltface is only .694", so it would be P14 bolt time again. I hate to lose the guide on the M30 bolt.
I have only actually held a Gibbs in my hand a couple of times, at SHOT Shows, etc. Jeffe, you are probably right...but that big hulking case calls to me from the Dark Side. On the bright side...I can wait until my PH actions get here and use the one with the .640" boltface and Gibbs size box, etc.


Stay tuned here gentle readers...next week we M-A-Y publish photos of said case. That is all I can say until I actually get (if they materialize) my fat little fingers on one...or two hundred, whatever!

my wife asked me to take her ring off cuzz she was going to clean and she could not get it off. she said "oh, i must be retaining water." i bravely thought to myself "no yer retaining fat"

Well, hooray! Five days later Ken came to his senses and changed it.

They need to correct that on the AHR page.

It is still made by Bertram though, isn't it?

I thought the 500 Jeffery had about 160 grains of water capacity.

That must be some thick Bertram brass in the AHR.

The 500 Mbogo will be very close to 150 grains. I don't recall what it is at 2.950". Will get it out to 2.990" eventually.

The cry of the night jar in the Tuli Block:

"Good Lord, deliver us."

When I see a 550 Gibbs I will be hearing night jars in my head.

quote:

It is still made by Bertram though, isn't it?

not sure...we need to get jamison to make it and the 500 mbogo 2.9"

if he made the 500 ahr short that would be great too...

o.k. i'll stop dreaming now

no no no...

not the 550 gibbs, the 550 cheyenne. stronger brass! the 505 gibbs cant handle it

550 cheyenne...aka tatonka masher.

Dr Berry

I haven't measured the rims or capacities on all 140 samples of 500 AHR I have but this data is gathered from 35 so it should have some statistical significance.

Mean Rim diameter: 0.590"
Mean case capacity (fully sized and trimmed to 2.87"): 163 gr H2O

FWIW

they should honor ken howells design and wishes with a .62" rim

this is why jamison needs to step in...

thanks for the info scotts...who made the brass???

Boomstick,

All 500 AHR brass, as far as I know, is Bertram. That is what all of mine are anyway, as well as, a few hundred others I know of.

The 500 Jeffery brass that I know of has a capacity ranging from ~ 152 to 158 gr on average depending upon manufacturer. If you guessed Bertram had the 152 gr you are a winner.

Scott,
You are welcome to participate in this thread. But, please don't call me Dr. Berry. Someone might get me confused with "Dr B" don't you know.

Thanks for the AHR rim diameter and Jeffery water capacity data, as well as confirming the brass maker.


Have you found any RL-10 for the light bullet loads in the 500A2 or 500AHR? You have instigated in my head an African Sheep Rifle load for the 500 Mbogo: 450 grain GSC HV at 2800 fps. I might have to build a second one with no freebore. Talk about versatility in a cartridge!

boom stick,
Get this straight: We are waiting for Marc Jamison to make 3.000" long Rigby basic (not 2.9") with only "Jamison" on the headstamp, though he might hopefully throw in "Mbogo" too, and the reloader could choose to engrave it either "470" or "500" to complete it.

Sorry RIP, this may affect your delicate sensibilities, but...twice fired cases measure within .001" of my reamer. Remember, I just duplicated the 510 Wells minus the irritating belt. I got three rounds off in seven seconds out of the monkey-rig stock and a 620gr cast bullet on top of 92gr of Varget. Boom-Boom-Boom!!
I bought 40 30-378Wby new pieces of brass at our little punkin roller gunshow today. I am going to build another 22-278Wby-AI for Rockchuck shooting next spring.

Projects, projects!

Rich

Rich,
Your .510 Kayser Express works great. That is great.

However, this reamer is not a .510 Wells with the belt removed. You are over simplifying. I will let it go at that, except to note that your reamer shows a shoulder of only 12 thou per side of step at the shoulder, and this makes the 500 Mbogo's 20 thou per side seem huge!

just enough shoulder to headspace on properly and work. With tutelage from my gunsmith I am doing much of the work, with that and some judicious horse-trading I am into this rifle well under $1000. Are there better .50 caliber DGR cartridges out there? Probably. Do I need more than 2400fps with a 600gr bullet? Doubtful. This cartridge can dish out more recoil than I care for, and will shoot clean thru two cape buffalo standing side-by-side, or an elephants' skull side-to-side and exit. It will break both shoulders and exit a Brown or Polar bear at 100 yards. It just does everything I planned for it to do, and at a working mans' budget. A CZ in 416 Rigby is a boring bar and rechambering away from one of these, and four down to boot. That's only about a $1000 bill for a total package DGR. I hope some other guys out there will be interested in building one. A Big Fifty at a reasonable price. Dies and brass are affordable, and anyone who casts lead alloy bullets, or has a friend that does, can shoot this thing at 2000+fps for about forty-cents a round. Cheap Thrills!

regards,

Rich

Why doesn't Jamison make 500 Jeffery brass without the rebated rim and call it the 500 JAMISON? Because he would have to pay Jeffery and Company royalties from his borrowing the original design. Does this sound familiar?

[QUOTE]Originally posted by RIP:
note that your reamer shows a shoulder of only 12 thou per side of step at the shoulder, and this makes the 500 Mbogo's 20 thou per side seem huge!


Ron,
are you comparing case drawings to reamer prints? You KNOW better... reamer print to reamer print, case drawing to case drawing..

I don't know what Kiff does for clearence on a DGR round.,, byt..

just a rough look at case spec,,,, one of rich's rounds would drop, directly, into a 510wells chamber... and PROBABLY be within headspace... assuming .003 tolerance/clearances on teh print.

jeffe

quote:

Originally posted by jeffeosso:
[QUOTE]Originally posted by RIP:
note that your reamer shows a shoulder of only 12 thou per side of step at the shoulder, and this makes the 500 Mbogo's 20 thou per side seem huge!


Ron,
are you comparing case drawings to reamer prints? You KNOW better... reamer print to reamer print, case drawing to case drawing..

I don't know what Kiff does for clearence on a DGR round.,, byt..

just a rough look at case spec,,,, one of rich's rounds would drop, directly, into a 510wells chamber... and PROBABLY be within headspace... assuming .003 tolerance/clearances on teh print.

jeffe

Jeffe,
I know the difference between chamber and brass specs. There are some places in the reamer specs that reflect what the brass is like and how it has to interact with the chamber, wouldn't you say? Like the shoulder angle and step? Also a reamer head diameter of .5900" is meant for a Rigby case head, not a Wells with the belt turned off, where the head is .582". The overall brass length is also longer for this reamer than a Wells reamer.

J.J. Donnelly must be totally out to lunch on his .510 wells brass specs if this reamer reflects a beltless .510 Wells. I am able to take into account chamber reamer versus brass specs.

If I try to resize .416 Rigby brass or .338 Lapua case heads (same thing) in my 500A2 dies, it doesn't work. It shaves brass when it gets down to the belt area. Seems to be about a .003" of brass is shaved by resizing the Rigby case in the 500A2 die. It creates a pseudo belt on the Rigby case.

Add the resizing die spec difference to the mix. As I understand it the dies have to be about .004" below max brass size to allow for the spring back of the brass.

Am I under-understanding something here?

Has Rich modified his Wells dies to eliminate the pseudo-belting brass shaving?

If they were in tolerance to size a .460 Weatherby case for the .510 Wells (diameter above the belt is .582" max), then they are too tight there to size a Rigby case that is .589" max though new brass may be only .585".

The larger belt recess in the die will not resize the end of the Rigby head.

.582" -.004" = .578" to allow for the .004" spring back.

New Norma or Lapua Rigby brass is .585", my Jamison is .587", CIP max is .589" at the head, .590" at the rim.

Shoving a .585" head into a .578" hole with a sharp 90 degree belt-stop-recess around the mouth of it will shave brass and create a pseudo belt on the case head.

How does Rich get around this?

I know how I do it when modifying 378 and 460 Weatherby dies, and .423 Dakota dies, and .338 Lapua dies to reload my .375, .423, and .458 Lapua RIPoffs.

My solution involves cutting, grinding and polishing a combination of .338 Lapua and .460 Wby dies, for the .458 Lapua, for example, and use of neck expander and neck sizing and crimping dies, home cooked, custom die sets. I only have to neck ream the .375 Lapua. The rest work without the neck inside reaming.

quote:

Originally posted by Idaho Sharpshooter:
just enough shoulder to headspace on properly and work. With tutelage from my gunsmith I am doing much of the work, with that and some judicious horse-trading I am into this rifle well under $1000. Are there better .50 caliber DGR cartridges out there? Probably. Do I need more than 2400fps with a 600gr bullet? Doubtful. This cartridge can dish out more recoil than I care for, and will shoot clean thru two cape buffalo standing side-by-side, or an elephants' skull side-to-side and exit. It will break both shoulders and exit a Brown or Polar bear at 100 yards. It just does everything I planned for it to do, and at a working mans' budget. A CZ in 416 Rigby is a boring bar and rechambering away from one of these, and four down to boot. That's only about a $1000 bill for a total package DGR. I hope some other guys out there will be interested in building one. A Big Fifty at a reasonable price. Dies and brass are affordable, and anyone who casts lead alloy bullets, or has a friend that does, can shoot this thing at 2000+fps for about forty-cents a round. Cheap Thrills!

regards,

Rich

Agreed, and ditto for the 500 Mbogo, but I would not rebore a CZ .416 Rigby that has a muzzle diameter of only .670" for a .510 caliber.

And just how do you use .510 Wells dies to resize fired .510 KE brass without shaving brass on the case heads down at the belt recess in the die, with a beltless case of greater head diameter? Please enlighten my delicate sensibilities.

I've posted this here before, page 414 of Ken Howell's book that I have yet to find an error in, the best book of brass specs there is:

The 500 Van Horn Express, made by turning the belts off of 460 Wby and shortening. Same page shows the 500 Wby, another me-too that Weatherby Themselves might have toyed with and never brought out:

Brass max dimensions I would say here, not reamer specs, just for comparison.

Copy the scan to a file and zoom in to read more easily.

These are over 30 years old, I think. Gil Van Horn was prolific.

thanks rip...

that drawing adds a lot of credulity to my beltless 500 a2 aka 500 a2 boom stick improved aka 500 boom stick.

the 500 van horn express is a 500 a2 bs improved short