Sounds very interesting Jeffe.

When you get that one in mass production, I'll have to have one, finally an over 50 for me.

Next you ought to do a 550 Nyati as a bolt action cartridge to go with the flanged DR cartridge.

Necking the .585 Nyati down to .550 and giving it a Gibbs sized rim ought to fix all the shortcomings of the .585 Nyati.

.550 Mbogo Flanged?
.550 Nyati Rimless?
.550 Nyati or Mbogo Flanged and Rimless?

Both of these would be based on the .577 NE case of course, as is the .585 Nyati.

Just some suggestions for whenever you get around to it.

Jeffe,
I am changing my vote to ".550 Mbogo Flanged."

Otherwise known as the 550 MF. I like it.

Jeffe,

I like ".550 Flanged". It adds a touch of nostalgia.

George

Jeffe,

For a classic style name for this round, then you must follow the way rounds were named in the past. The parent case is the 577 NE, so it should be part of the new cartridge name. 577/550 NE

Hog Killer

PS: or you could call it the "550 Osso"

I voted 550 Flanged, although I like the thought of a headstamp that reads "550 M-F."

here's what i'll be building it off
First picture aint mine.,, it's the same thing, just with better finish. the second one should be in saturday, and it is mine..

second one is
yep, it's plain plain...

roger can fix that for me...

it's also built like a BSH.. double lugs, greener third, side clips, and a belgian

wood? sucks.. but, then again, i'll fix that too!!!


I'll be building a single piece monoblock from 4140, and using 4140 barrels.. according to ellis brown's forumla, it will be good to 35kpsi... would like it to be well under that.

Jeffe,
I forgot all about the 550 flanged. Do you still need some turned brass. I've got some 50 bmg brass to finish turning this weekend for ED Hubble and while I'm set up I can make yours if you still need it. John

I've always liked the sound of flanged, don't know why, but it has a good ring to it. Which reminds me I'd still like to build a 350 flanged, the 375 flanged run through the 350 Rigby die. It would rather fun in a falling block, and very nice in a double.

Jeff if you would want a straight case, that is long, I can make you some out of 475 #2.
Base .580 - mouth OD .568- not much taper-
3.5 in long.Or if you wanted long and more taper
and could get some long basic 577 brass, I could
make a straight case about .625 base and .572
mouth OD.And John could also make you long ones
about .630 base and .584 mouth OD, that would be good for 35k. The longer, the more they hold of slower powder. Keep pressures down.Staight is the way with all the other 550 cases straight, and big NE cases straight.Ed.

Don't like .550 MF? How about:
.550 Bibamofla
short for
.550 Big Bad Mother Flanged

Nice wholesome moniker.
This takes the obscenity out of Lazzeroni's .475 Bibamofu.

quote:

For a classic style name for this round, then you must follow the way rounds were named in the past. The parent case is the 577 NE, so it should be part of the new cartridge name. 577/550 NE

I agree with that. In addition it saves any confusion as to it being a rimmed version of the 550 magnum.

Mike

All kidding aside, I was first to cast a vote for 577/550 Nitro, and I agree that is the only way to go:

.577/.550 Nitro Express. There will be no confusion. Screw the competition with their oddball names.

quote:

Originally posted by RIP:

.577/.550 Nitro Express. There will be no confusion. Screw the competition with their oddball names.

1

Only way to go.

If you call it just the .577/.550 you risk confusing it with the old .577 round (ie same as the .577/.450), rather than the .577 NE.

By the way, can anyone create a NEW Nitro Express round? Is the name proprietory in any way?

Right, the 577/550 flanged magnum nitroexpress

PaulH, A very nice Gibbs boxlock in 350 Rigby No. 2 came into my hands in 1984 on a posting in South Africa with me a novice at handloading. Only recipe found to make the right brass was to form from 9.3x74R brass and that involved buying form dies from the Aussie dealer John Saunders (whom I met in Melbourne just last November)and arcane practices like neck reaming. Never thought of just running a .375 flanged thru the sizing die - didn't know quite what a .375 flanged was in those days...
Regards, Tim

NitroX,
I am sure there is nothing proprietary about "Nitro Express." Even Mark Sullivan uses it as a name for his biz. You too in shorthand handle. It is just a general descriptive term for those cartridges that carry the mail like an express train.

The .404 Jeffery Rimless Nitro Express is another name for the .404 Jeffery, etc.

Jeffe really ought to go for it. "Flanged" might be redundant since the .577 basis covers that too.

".577/.550 Flanged Nitro Express" would sure make it clear, eh?

TECHNICALLY
it's the 577/500/550 Nitro, as it's made from 577/500 parent brass.. which is NOT 577 brass exactly...

As the 375 HH flanged was meant to designate from the 375 HH magnum (you couldn't get a flanged INTO a magnum gun, or close a gun on the wrong way round) I thought this to be a darn good homage...

For those in the know, until lately, no one would have thought to put a belted round into a double.

I am still listening.. and 550 MF cracks me up.

the 577/500 has a thicker rim, a smaller rim diamater and a .01 narrower base diameter than the 577 3" nitro express

jeffe

Jeffe,
If it must be 577/500/550 Flanged Nitro Express, then maybe "550 MF" ain't so bad after all?

Flanged is leadidng the pack in votes...

Magnum
Express
Flanged

what a perfect trio!!!

jeffe

550 Flanged is a 550 F-er. Brass stamped ".550 F." works for me.

550 Flanged it is..
thanks all

jeffe

jeffe,

Is this essentialy the 585 necked to 550.

Mike

Mike,
essentially... but not exactly..

the 577/500 3 1/8" nitro has a smaller and thicker rim, and a slightly smaller max base (.650)

the case will be a slightly "improved" 577/500 with the shoulder diameter moved a hair out, and a hair forward, resulting in a 1 caliber neck... why 1 cal neck? That's the only thing in nitro rounds that i don't like the "look" of, and with a good crimp, it will hold.

besides, it's MORE case capacity and less taper (still have .043 in 2.4 inches (.215 per foot)) which should result in lower pressure and bolt thrust.

my thoughts are that this will have >180gr of H2O capacity, and will operate around 28,500 psi. My pressure trace will help with this.

jeffe

Jeffe, did you get the pressure trace? I think it will be interesting to see if you get the larger secondary pressure spikes from the slower burning powders.
I've been thinking about doing a 470 NE on an Enfield just for pressure testing. I wish Bauska would make the 470 barrels already. I don't even remember how many months ago we ordered them.

Quickload shows the 577 3" haveing 185gns H2O capacity.

I went to www.mountainmolds.com and used his online bullet design program to get an idea of bullet lengths for different weights to plug into quickload.
A custom bullet mold might be a nice addition to your project for cheap practice projectiles.

Lars,
I got the pressure trace, and I'll be measuring fired cases.. the 577/500, iirc also reads 174 grains, which i am "improving"

I think i am going to be sending the leige back... it was a little orver represented... i guess the JB weld holding the front swivel on toppped it for me... yes, i didnt buy it for it's total shotgun value... but I expected a SHOTGUN sin embargo

jeffe

You might need a neck brace to survive the recoil of this big boomer.