Here is a fuzzy pic comparison, of 500 Jeffery vs. 500 Mbogo. The good camera ran off to San Diego for a few days:



HA!/DOA is reorganizing as RIP Arms, Inc.: "Home of the Lapua and Mbogo RIPoffs."

A new cartridge board will be coming soon, but the 500 Mbogo can be visually compared to the .505 Gibbs below:



The 500 Mbogo: Not a nostalgia trip.

she's a beauuuuuuuty! (in my best "crockodile hunter voice)

the 500 mbogo lives!

good going rip. wish you luck and fun putting the rifle together

Thanks, Boomer.

This is the RIPoff recipe for a 500 Mbogo:

BRNO ZKK 602 action with PME 3-pos safety.

McMillan stock.

McGowen 10" twist stainless barrel with integral lump recoil lug and rear sight island, .820" at 28" crown, to be shortened to 24":


Chamber with 470 Mbogo reamer and 50-cal pilot.
Ream the neck and throat with Dave Manson neck&throat reamer.

Fireform 470 Mbogo brass to 500 Mbogo.

Get custom dies made from formed brass, and while waiting for those use .475 to .510 neck expander and dies for 500 A-Square, 500 Jeffery, .505 Gibbs and 470 Mbogo to "make do."

Engrave "500/" ahead of "470" on brass.

Stamp barrel "500/470 Mbogo" by the "American" not "British" convention.

That's a wrap, er, RIP, or RIPoff.

Looks like plenty of shoulder!!! Much more than I think there would be left from a .416 Rigby piece of brass!

easier to feed than a 500 jeffe, about the same room as a 510 wells, no belt, and pretty cool looking

jeffe

quote:

Originally posted by jeffeosso:
easier to feed than a 500 jeffe, about the same room as a 510 wells, no belt, and pretty cool looking

jeffe

Looks good, but Jeffrey just sounds goods. If for no other reason than "old time sake."

quote:

Originally posted by jeffeosso:
easier to feed than a 500 jeffe, about the same room as a 510 wells, no belt, and pretty cool looking

jeffe

Jawohl, a leetle beet more capacity than the .510 Wells, und a leetle beet more capacity than the 500A2 too.

After all, eet eez 2.950" to 3.000" long een the brass und .575" broad een the shoulder, as beeg as one can make eet on a .416 Reegby basic case. The neck will be .45 (meeneemum) to .50 (maxeemum) eenches long too, depeending on how long the brass stretches.

500/470 Mbogo brass ees 2.950" at birth.
Treem to 2.990" eef eet ever gets to 3.000".

Maybe I weel have to build a 500 Jeffery, or 12.7x70mm Schuler, just so I may have some laughs for auld angst.

It is a sexy beast, isn't it?

The shoulder looks pretty darn good.

Methinks this may be my next big bore, RIP. Not that I ever thought it was a bad idea, but you have persuaded me. I couldn't justify in my mind actually creating it, but now that it exists I don't have to.

Headstamped 500 Mbogo brass would go a long way to selling this idea. Keep brass kissing, RIP!

Cheers,
Canuck

I did section a piece of Jamison brass and compared it to the Quality Cartidge, both headstamped "470 Mbogo":

Quality Cartridge 470 Mbogo appears to be made from Norma .416 Rigby basic.

Jamison brass (470 Mbogo and .416 Rigby)is thicker in the head than Norma .416 Rigby brass, by a little bit, but not quite so thick as the Lapua-made .338 Lapua Magnum brass.

I love it.

quote:

Originally posted by Bwana-be:
I love it.

Thanks. This new kid on the block could do 2500 fps with 600 grainers, but I like the idea of a gentle and effective 570 grains at 2400 fps and low pressure, about 50Kpsi.

With an FN or FP solid it will make Texas/Portuguese Heart Shots on elephant a sure thing.

It will have less recoil and safer bolt thrust than either the 500 Jeffery or .505 Gibbs, assuming same muzzle output and rifle weight for all three of these dancing on the head of a pin.

So, what's the taper? Shoulder angle? Neck thickness?

quote:

Originally posted by Bwana-be:
So, what's the taper? Shoulder angle? Neck thickness?

500/470 Mbogo taper of the case body is .016" for the base to shoulder run of 2.480".

404 Jeffery body taper is .015" for a 2.001" run.

500 Jeffery body taper is .016" for a 2.321" run.

As "thou-per-inch":

500/470 Mbogo = 6.5
500 Jeffery = 6.9
404 Jeffery = 7.5

It is a minimum taper case, but it works fine on the 470 Mbogo with 500 grainers up to 2685 fps causing no extraction stickiness at all.

Neck diameter of my dummies is 0.531" with a .509" bullet seated. The neck reamer will be 0.535" diameter.

The reamer shoulder diameter is 0.575" (same as 470 Mbogo, of course, same reamer), so the step at shoulder-to-neck is .040" diameter difference, or .020" per side, radial difference. Its shoulder is visible and palpable and more than some other cartridges like the 10.75x68mm Mauser or the .411 Hawk.

Shoulder angle is same as the 470 Mbogo, of course: 35 degrees semi-angle, or 35 degrees per side.

RIPoff'ed from Dave Estergaard's 470 Mbogo. Just neck it up.

It will work fine, no doubt.

I am back to my so-called 20/20 rule for minimum shoulders on wildcats: 20 thou and 20 degrees per side.

6.5 thou per inch taper is the "least taper cartridge" experience for me, and it has been a good one, with the 470 Mbogo, no feeding nor extraction problems.

Some say the minimum taper produces less bolt thrust and less brass stretching.

It is surprising to compare the minimal tapers above to a couple of very tapered case bodies:

.416 Rigby: .050" for 2.353" = 21.2 thou per inch

.505 Gibbs: .040" for 2.458" = 16.3 thou per inch

The .404 Jeffery gives the overall impression of a lot of taper with its long neck and sloping 8.5 degree shoulder semi-angle, but it has very little body taper.

The .338 Lapua has essentially the same giant body taper as the .416 Rigby, and a 20 degree shoulder to boot to make it friendly to a semi-auto military application.

This makes the Lapua RIPoff cartridges slick feeders and extractors in machineguns too.

The minimum taper and 35 degree shoulders of the 500 and 470 Mbogo may not make the best squad automatic, but they work fine in a bolt action rifle as far as I can tell, from my limited experience ... that will get greater in the future.

.040 .. 35deg ...
yep, it'll work.. works for the 470 ar, though it's NOT huge

good work, ron
jeffe

quote:

Originally posted by jeffeosso:
.040 .. 35deg ...
yep, it'll work.. works for the 470 ar, though it's NOT huge

good work, ron
jeffe

Ah so! Thank you very much. Proof positive in the 470 AR.

Hummmmm, 500Mbogo. It does have a nice "ring" to it.

Oh well any .500 bolt gun will have to wait till after "Li'l Bubba" gets built first. I guess a 416 Rigby RSM would make a starting place for "Cousin Bubba".(being a RSM, instead of a Model 30S) Long throated for BMG bullets, weighing about 15 lbs, good scope, a true loooong range "varmit" popper.

Hog Killer

Good work brother Ron,

Prolly' want a "sniper fill" on the McMillan stock.

LD

Thanks y'all, just another RIPoff.

You can actually see the difference in taper (and lengths, dotted lines 1/2" apart, solid lines 1 cm apart) in the photo below, left to right:

1) .423 Dakota-Lapua (it is a short one, trim to 2.480" brass, 2.490" max)

2) .423/.338 Lapua Magnum (Lapua-RIPoff, 2.720" max)

3) 500/470 Mbogo (Mbogo-RIPoff, 3.000" max)



(First peek at .423 Dakota thread is showing no interest, another chance to show my lack of photographic capability at present ... just waiting for John The Greek to tell me how "peculiar" this one is.)

is the 423 dakota you show the one comming from dakota or your own creation?

if from dakota it could be a good candidate to make the 500 a.r.

Boomer,
The short one is the .423 Dakota from Dakota.
The shoulder diameter of the .423 Dakota is only .547" and the shoulder semi-angle is 35 degrees.

You will have to blow that shoulder out to .575" (like the Mbogo) to neck it up to "50" cal.

Have at it.