Yes ,,this is a cartridge which of few owns and load for,,,why ??
In my opnion i wonder why it's not listed on board?
I also would think it is really silly if people tell me this cartridge wont perform any better than the .460 Wby. Then i can understand why it's not of any use !
I have seen the most impressive load datas on this one,,but their not correct acccording to most peoples experience. As they list 2980 fps with a 500 grain bullet,,i find that load so rediciously excessive,,but i think it will perform with a 500 gr.in the middle of this ABSOLUTE NUTCASELOAD and original weatherby factory ammo,,rated at 2600 fps@500 gr.CAN ANYONE PLEASE TELL ME MORE ABOUT THEIR EXP. WITH THIS CARTRIDGE,,,INFO WOULD BE GREAT,,OF ANY SORT !

Its basically a belted one of these... www.470mbogo.com

I'd rather have a 470 Mbogo any day (and I do!). Anyone that tries to get 2900+fps with a 500 grain bullet from this kind of case is either very brave or stupid. 2600 is easily attainable from a 24" barrel though. You might do even better than that, although you'd really have to wonder why?

The fellow that posts here as 470Mbogo has extensive experience with this cartridge and can better answer your questions. Unfortunately he is "out of town" at the moment. Hopefully he can check in here occassionally though.

Cheers,
Canuck

[ 03-14-2003, 05:57: Message edited by: Canuck ]

Yea, the 475 A&M data comes from the days when many velocities were "Estimated". Very few chronographs around back in those days. Don't believe everything you read in Ackley's books or the old gun magazines.

John-They did chronograph them, but they built them on real strong actions, so they figured
70-80,000 psi was a good operating range.They really tested the cases with their high loadings.
Ed.

I would much rather have a 470 Mbogo or a 475/416 like is on the reloading pages of this site.

Ken-Yes that's better,Loading rifles with
blue-pill loads is scary.Ed.

No wonder the recoil was high!!

First A&M I saw was on a P-17, I would not touch off a 80,000 plus psi load in one.

I have pressure measuring equipment, and touched off a 84,000 psi load once in a 340 Weatherby. Impressive recoil to say the least (nope, it was not a Weatherby action!). Had to use the barrel vise and action wrench to get the bolt open, required removal of the barrel. Brass flowed like a chocolate candy bar left on a dashboard in July, really locked things up.

Now, if I can just improve this method a little, should be a quick way to form brass for those big cartridges we all like.

I really do not trust those old chrono readings, most were made with the Avtron vacuum tube chrono's where you had to count the lights and look up the velocity on a table. We were using one in the Mid 60's. And a little fudging on screen spacing can give you any number you want, I have caught guys doing this with modern chrono's. Back in the wildcat craze of the 50's and 60's quoting high velocities was the thing to do.

I think they used actions they built.But they still were stressing the brass too much.As John
said some were built on Enfields.Safe loads of
60,000 psi in 24 inch barrel
would be around 2700 fps with 500 gr.To get the
extra 200+ fps with powders used in those necked cases takes over 12,000 psi more......And if you added 4 inches of barrel instead, you would have 150 fps extra!!....Ed.

Yes Hubel,,that would be my goal !!!

I have always wanted a cartridge to make 2700 fps at the muzzle with a 500 gr.bullet.
I did not quite understand what you meant by adding 4 inches on the barrel lenght.
Say if i choose to rebarrel my gun to .475 A&M Magnum and the lenght of barrel is 26 inches,,,then what would the pressure be like,,on the action,,and still make 2700 fps + !!
what powder,,,what action would you choose ?

You say a .475 A&M Magnum with a 28 inch barrel and pressures operating at 72,000 psi,,would send a 500 gr. to 2900-3000 fps,,right !?

Per-If you had 26 inch barrel you could get a
500 gr to 2700fps at 60,000 psi or little less.
Use IMR 4350 or WW-760 starting at 110 gr and work up.I like Ball powder the best.

With 28-30 in barrel and 72,000 plus pressure you could get 2900 fps.But as I said before that stresses brass to much.

For your project any good magnum action will
work, Ruger, CZ, Montana. etc...Ed.

FWIW- I played with a 460WBY for awhile trying to actually see 2700fps with a 500 gr solid. The best I ever got was a honest 2650fps and I observed the belt expansion was .006 inches!!! This was with new brass and I quit right there and then! I've run into folks who say they routinely hit 2700 in the WBY, but they don't crimp and don't seem too worried about this level of belt expansion.
I really second Cannuck's comments on the 470 MBOGO. I've built two of them so far and this round gets pretty close to my idea of a good backup round to the .600 OK.Only because you can get more 470 MBOGO's in the mag box though!
If you like hammering open your action, I'm sure you could build a 470MBOGO on a Mcmillan .50 BMG action ( They do make custom order .590 bolts) and really crank up the pressure! You probably could get away with low to mid 70KPSI loads and one or two shots before the brass failed. I will be pleased to observe from a safe distance!-Rob

Rob & Per--A lot of the early wildcatters were
satisfied with 1-2 reloads.Thats why they loaded
way heavy.

I never could see it. Keith, O'Neal,
and Hopkins made wonderful wildcats, that ran decent pressures and could get a number of reloads.The 475 OKH a forerunner of many others,
like 470 Capstick, was a great early cartridge.
And pressures were decent. Ed.

I think we are missing something here.

True, you can over load just about anything and obtain high velocities. But not only is it hard on the cases, it also is hard on the action.

However, as I see a Big Bore DGR, the purpose is to have a rifle that runs at medium pressures, does not have sticky bolt lift, and is reliable. Who wants a rifle that you cannot extract a case out of when you touch off a round in some hot African valley where both the rifle and the cartridges have baked in the sun????? Or run the risk of a case failure? Even a pierced primer can ruin your day. 60,000 psi is way up there for big cases with lots of rear internal case area, run some bolt lug force calculations and make up your own mind.

Hunter Jim may pipe in and mention some of the results for rifle tests in the Hot Zim Summer during the PH Tests.

Besides, it has been said many times here and in other places that most bullets perform adequately at a tops of 2400 to 2500 ft/sec.

As a rifle builder, I consider safety and reliability at the top of the list. Chasing high velocities is best left to the shooting range.

If you have not done so, read Taylor's "African Rifles and Cartridges" and pay attention to what John says.

John- Couldn't agree more! That's why the .600 OK is designed for a max of 55KPSI and uses a three groove barrel and freebore. A blown case/action is a terrible way to waste a perfectly good hunter!-Rob

A little story and a comment...

In 1972 the Custom Gun Shop in Edmonton Alberta built a .475 A & M using a Marquart barrel, on a Weatherby Mk-V action. (Doug Paul did the 'smithing.) They also loaded some 600 gr. ammo for the customer, who lived in B.C.

A couple of weeks after being shipped, it was back. Customer "changed his mind". So Lance Paul (Doug's son) who was a recent grad of Colo School of Trades 'smithing curriculum, and I took it to Sherwood Park range just to try it out. With us was a truck driver by name of Chuck M---.

Lance, who likely weighed 130 pounds with all the clothes on that he owned, sopping wet, fired the first round. "Impressive..." he said. I fired the second round. "More than I want to shoot!", I said. (My .450 Ackley wasn't NEARLY as severe as that .475 A&M.)

Chuck wanted to shoot the rifle. I handed it to him. He put it up, and welded his nose to his right thumb, preparing to take his shot. "Uh, Chuck...you might not want your nose against your thumb..." Lance & I both started to say. Chuck replied, "Leave me alone, I've fired lots of big rifles...KABOOM!!"

[ 03-21-2003, 03:39: Message edited by: Alberta Canuck ]

Don't know why, but my computer keeps posting when I hit the space bar...

Anyway, Chuck had fired the rifle and had a stunned look on his face. His nose was also pouring blood, and within about two minutes was double its normal size.

That ended my desire to ever own a bolt action .475 A&M...it had severely greater recoil than my .450 Ackley Mag, at least as stocked by Weatherby for the Mk V. It also was MUCH worse to shoot than my doubles, which included such items as .577 and .470 Nitros.

Lance fired the remainder of that box of ammo.

COMMENT - John Taylor's books are interesting, but "African Rifles & Cartridges" does seem to have some errors. For instance, he says bullet diameter for the .470 is .483". Well, mine weren't. They took .475" diameter bullets.

[ 03-21-2003, 03:25: Message edited by: Alberta Canuck ]

P.O. Ackley simply used Mauser actions and loaded them until the primer blew then back off one or two grains....He did not use a special action...

One thing missing in this topic is the shootability of a DGR cartridge. The 470 Mbogo cartridge with a 500 grain bullet at 2500 fps from a straight stocked 10.5 lb rifle with a good recoil pad is a very shootable cartridge. If you push the cartridge to it's max velocity you take chances of high pressures lock up in hot temperatures. This takes the reliability out of any cartridge and just doesn't make any sense. The power of a 500 grain .475 bullet at 2500 fps really has to be seen to be appreciated. This is more than enough and has a good comfort and good reliability factor built in. From the information I've been able to find the 475 A&M is just the 460 Weatherby necked up and nothing else. The 470 Mbogo has a staighter case and is longer in body lenth than the 460 Weatherby. There are comparrison pictures of the 460 Weatherby and the 470 Mbogo on my site @ www.470mbogo.com.
Take good care,
470 Mbogo

You are right on .475 A&M derivation. The .475 A&M I fired was nothing more or less than the .460 Wby necked up to take 600 gr. .475" bullets. Many shooters of the day used 500 gr. .475" bullets in theirs.

Personally, I'd still take even a utility-grade .470 Nitro any day over the .475 A&M for 95% of applications.

AC

AC

[ 04-01-2003, 01:01: Message edited by: Alberta Canuck ]

Hey Hubel !! what kind of powders will you reach 2700 fps and 500 gr. bullets in this caliber ?

What ballistics Alberta, did they get with 600 grainers in this caliber , 2500 fps ?!

PER--Use ball powders and decent barrel
lengths.Ed

Sorry I can't help you with the ballistics. If we chrono'd that load, I don't remember the results.

Somehow, I doubt we did. In those days all I had for a chrono was a Hollywood chrono...it required shooting through screens which were basically a clear tape with silver electrical conduction lines painted on it. Required clipping pieces of tape and putting them between alligator clips on both the start screen and the stop screen. Each tape was good for 1 (one!) shot...then you had to change tapes. You could also use a piece of pencil lead as a screen, but more often than not you'd miss one of the two leads (one for start screen, one for stop screen) each time you fired, if not using a machine rest. That would waste a LOT of pencil leads, waste a lot of time, and give a lot of erroneous readings. Strips of aluminum foil would work as screens also, but they were very fragile and a PITA to work with.

So, usually, we would not chrono unless it was a cartridge we really cared to keep and use. The particular .475 A & M used in this experience was just put back on the shelf and sold. I don't recall who bought it, but think it might have been Marv Harwood, a well-known Alberta double rifle afficianado of the day (and very nice guy)who enjoyed shooting anything really big or "interesting". I think Marv has either just retired from, or is nearing retirement from, the Calgary PD where he has been a member of their SWAT team for some years.

Best wishes,

AC

[ 04-03-2003, 01:52: Message edited by: Alberta Canuck ]

All this talk of chronos has me wondering how the measurements were taken back in the old days- kynoch ammo in the NE rounds etc.
I remember reading something about calculating velocity by shooting pendulums and measuring all that tricky momentum stuff.
Or was this an even older method?

Karl

It is raining here today.

code:

---

As check, used 460 Wby data from Hodgdon #27:
26" barrel, 500g HYD RN, COL=3.72"
Used Accuload to convert cups to PSI
49.9kPS I= 42.2CUP, case capacity = 141.5g
 
IMR7828_117g_2360fps@41.8kcup for Manual
                    @49.3kpsi conversion
IMR7828_117g_2471fps@51.0kpsi Quickload
 
for 157.4g case capacity to calibrate pressure
 
IMR7828_117g_2360fps@40.6kpsi Quickload
 
Okay, Quickload estimate for 460 Wby is 
about 21% low for peak pressure for IMR7828.
 
For 460 Wby and H4350, 500g HYD RN, COL= 3.71"
 
H4350_115g_2508fps@????? for Manual
           2593fps@60.4kpsi  Quickload
 
I made a model for the 475AM in Quickload 
using Donnelly for dimensions and 143.74g
capacity and COL= 3.75"
 
H4350_115g_2448fps@45.2kpsi Quickload
    139.8g_2980fps@94.5kpsi Quickload
 
and for  IMR7828 and load density =127%
 
IMR7828_146.2g_2980fps@91.8kpsi Quickload 

---

Simulation indicates that good possibility that the 475 A&M for 500g RN and 2980fps was around
91,800 *1.21 = 110,000 PSI!!

So, either these gentlemen had the cujones of the Cape or wishfull thinking.

steve505

There are lots of ways to build chronographs.

The simplest and earliest is probably the ballistic pendulum. Basically that requires hanging a weight (mass) from a pivot point, then shooting into the weight and measuring how much it moves. With that measurement it is easy using relatively simple math to calculate the speed of the bullet fired into the weight.

The tough part is that one needs to know the EXACT weight of the pendulum, and the EXACT length of the weight's distance from the pivot point. It is also necessary to include in the weight of the pendulum the weight of a "marker" moved by the pendulum's motion, so one can easily check EXACTLY how far the pendulum moved...and you'll still be off by the amount of energy absorbed by the friction involved in moving the marker. That, however, is really not too important, as relative velocity is often what we are after anyway, not exact true velocity. I'm not certain what method was used for the very first chronographs, but I suspect they were ballistic pendulums.

A second method (and one of the older ways) to build a chronograph is to use a "spark" system. With that method, a grounded metal disc is rotated at a very high, known, constant, rpm. The metal disc has a thin, replaceable, paper disc attached to its face. When the first screen is broken by a bullet passing through it, an electric circuit is closed. The electricity of this circuit is of higher amperage than in a counter chronograph, and the electricity is carried through a fine flexible metal pointer which rides against the surface of the paper disc. The higher amperage current "burns" a line into the paper disc so long as the circuit is closed.

When the bullet passes through the "stop" screen, the flow of electricity, and the burning of the paper disc, both stop. To calculate the speed of the bullet, one need know only the speed at which the disc was rotating and the length of the line burned in the paper disc. The calculation is then just simple math.

The farther the burned line is from the center of the rotating paper disc, BTW, the more accurate the measurement will be, because the length of the line will be longer, and therefore more easily measured or "read". That is, an error of .01" in the reading is not nearly so important in a line 5.50" long as it would be in a line only .55" long. This method, incidentally, was reportedly the one first used to calculate the speed of light. A light beam was "shot" through the screens rather than a bullet.

A third and later way was to use a condensor to store an electrical charge fed into the system during the time the circuit was closed. The "size" of the stored charge indicated how long the circuit had been closed, and therefore how long it had taken the bullet to go from the start screen to the stop screen. The Hollywood which I had was one of these and operated off the 6-volt battery of your car (in those days cars were mostly all 6-volt, rather than today's 12-volt systems). With the first Hollywoods you got the actual charge figures and had to look up the corresponding speed in a table provided with the chronograph. Later Hollywoods displayed bullet speed on a face similar to that of a voltmeter or ampmeter...which is actually what it was, just with speed figures in place of amp figures.

A fourth and still more recent way to build a chronograph is by running an electric current through a crystal with a known vibration rate. That is the way electric watches work. Basically, they are what is known as a "counter" chronograph. If a quartz crystal vibrates at, say, 80,000 times per second when electrically excited, then the mechanics of the watch are built to move the second hand a distance on the watch face marked as 1 second, for every 80,000 vibrations of the crystal.

Making a chronograph by this method simply requires building a machine to count the number of vibrations while the circuit is closed...it closes when the bullet cuts the first "screen" ("start" screen), and opens when the bullet cuts the second screen ("stop" screen). They are called start and stop screens because counting of the vibrations starts when when cutting the first screen provides electricity to start the crystal vibrating, and when cutting the second screen stops the flow of electricity so there are no more vibrations of the crystal.

This is the way most of the fourth generation somewhat-portable chronographs worked. "Potter" brand chronographs were the most famous (and expensive) of the early models of that type, coming into use as early as the 1950's. They were used for clocking everything from bullets to drag races...not to mention the Indianapolis
500 as well.

Anyway, current modern chrnographs are just sophisticated "counter" chronographs, similar in principal to the old Potters, but with solid state circuitry, modern "chips" to do the counting and conversion to bullet speed, and LED displays to exhibit that speed to the user.

All of this is from memory of an old guy, so please excuse any minor errors.

Best wishes,

AC

[ 04-18-2003, 00:39: Message edited by: Alberta Canuck ]

AC,
Very interesting history of chronographs. I have an Ohler 35P and I think the crystal in it viberates a million times a second. That is really hard to fathom that something can be that fast. I guess the faster the crystal the better the accuracy.
Take care,
Dave

Ac the ballistic pendulum was what I was thinking of then for the 19th century arms.

Karl

Karl - I thought maybe it was...and you were dead on. For many years even major arms & ammunition companies relied on ballistic pendula for their velocity figures.

470 M'bogo - You're welcome. I will have to go back and research my library a bit when I get the time, but I think Dr. Oehler had a working relationship with Potter at one time early on. That may be just a "senior moment" on my part, but I think that was the case...it may well be that Dr. Oehler at one time worked FOR Potter, but I won't stretch my memory enough to say for sure that is correct.

(N.B.: My memory IS absolutely perfect!! Unfortunately, it is only 0,0000017644413" long! Or, is that something else I don't use much anymore?....hhmmm...)

AC

[ 04-18-2003, 00:51: Message edited by: Alberta Canuck ]

Because, according to Ackley, "It is overpowered for anything on this planet since the demise of Tyrannosaurus Rex, and until safaris are possibe to Mars or other planets, it has little practical use" ....