Todd E. was making some good points, on the 500 Jeffery thread, about inadequate shoulder of a cartridge contributing to headspace problems and case head separation potential.

As the big bore cartridge case gets bigger and the shoulder angle less abrupt, even more shoulder to neck measurement difference would possibly be required.

I would like to have some input from the experts or the amateurs, like me, on just what a minimum safe shoulder is.

Surely the 400 Whelen is controversial for inadequate shoulder, but is an improved version of it O.K.?

What are the measurements of some cartridges that are rather small shouldered but adequate?

For the difference: Shoulder diameter minus neck diameter. Divide this by two and that is the step down of the shoulder-neck junction.

I just looked at the 460 G&A article in the Nov. 2001 G&A magazine and noted the shoulder to neck difference to be 0.050". The shoulder angle is only 15 degrees.

This is a shoulder of only 0.025". This cartridge has a flawless reputation, supposed to be the ultimate DGR cartridge, etc.... It has a rather shallow/acute shoulder angle too.

Would this be a place to hang the hat? Minimum shoulder of 0.025" step down?

I will get back later with the actual diameters and shoulder angle in degrees.

Can anyone else look up some specifications or measure some cases? Fireformed in good chambers would seem best if measured.

I can do this later but don't have access to my references right now.

Cases of interest (or any others that might be brought to our attention):

460 G&A
404 Jeffery
585 Nyati
400 Whelen
400 Whelen Improved
470 Mbogo
505/416 Rigby (full length or shortened?)
475/416 Rigby

What are the measurements for:
shoulder diameter
neck diameter
shoulder angle?

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RAB

[This message has been edited by R. A. Berry (edited 10-21-2001).]

RAB,

My point was specific to the 10.75X68. I mentioned the Nyati solely because of the discussion concerning soft brass. My concern being that the soft brass would extrude easily and therefore, with when the striker hits the primer it may set back the shoulder creating excessive head space. Your observations are sound however as many of the popular wildcat big bores have in my opinion insufficient shoulders. I can provide you with some of the dimensional data your requested:

585 Nyati:
Shoulder diameter - 0.650"
Neck diameter - 0.605"
Shoulder angle - 20 deg

404 Jeffery
Shoulder diameter - 0.518"
Neck diameter - 0.434"
Shoulder angle - ???

400 Whelen
Shoulder diameter - 0.462"
Neck diameter - 0.436"
Shoulder angle - 17.5 deg

400 Whelen - Ackley Improved
Shoulder diameter - 0.462"
Neck diameter - 0.436"
Shoulder angle - 40 degrees

10.75x68 Mauser
Shoulder Diameter - 0.470"
Neck diameter - 0.445"
Shoulder angle - 20.5 deg (?)

458 Imperial MAg
Shoulder diameter - 0.53"
Neck diamter - 0.485"
Shoulder angle - 30 deg

450 Rigby
Shoulder diameter - 0.540"
Neck Diameter - 0.475"
Shoulder angle - 45 deg

475 Rigby (not improved)
Shoulder diameter - 0.540"
Neck diameter - 0.505"
Shoulder angle - 45 deg

475 Rigby Improved
Shoulder diameter - 0.560"
Neck diamter - 0.505"
Shoulder angle 45 deg

Those are all I have dimensions on. Please do not beat me up too badly if some one elses dimensions are somewhat different. Remember that many of these are wildcats and therefore not standardized! As you can see the 10.75X68 Mauser actually has 0.001" less shoulder area than the 400 Whelen which no self respecting American riflemen would ever shoot (just kidding). I suspect however that the Mauser suffers from some of the same issues. By the way I consider the 450 Rigby to have a bare minimum shoulder and much prefer the 450 Dakota which is an improved Rigby case i.e. has a shoulder diameter of 0.560". For the same reasons I would not use a 460 G&A. Just my opinion on those last two though.

For me I consider a minimum acceptable shoulder to be 0.030" per side (that would be a difference between neck and shoulder diameters of 0.060") with a minimum shoulder angle of 25 degrees.

Todd E

[This message has been edited by Todd E (edited 10-20-2001).]

Todd,
I think your post is correct concerning the 10.75x68, particularly with the soft brass available from Bertram...I have seen a sharp shoulder rounded by firing, and that HAS to be your concept, no other explanation..I was concerned enough to re-chamber to 404 Jefferys and install a new long obendorf box

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

[QUOTE]Originally posted by Atkinson:
Hi Ray,
Why don't you try firing just a primed case to see if the firing pin striking the primer changes the shoulder of your soft case. You could put some dye or smoke the case shoulder to see if the shoulder is driven forward. 470 Mbogo

Todd E,
Thanks for the info!

Forgive me for leading anyone astray on the 460 G&A. I went back and corrected my previous dyslexic data, typed off in a hurry and now seen to be wrong.

460 G&A:

Shouder diameter 0.530"

Neck diameter 0.480"

difference 0.050"...or 0.025" stepdown

Shoulder angle 15 degrees in the drawing, 30 degrees in the text of the G&A article and they said the 30 degree angle was the same as the 404 Jeffery, but the shoulder was just moved muzzleward and blown out some.

So it is close to your 0.030" stepdown recommendation but it does not make the 25 degree limit.

Let's just call this stepdown per side the shoulder measurement, which is included with angle to describe the shoulder. So the listed cartridges are as follows:

460 G&A 0.0250" 15.0/30.0 degrees
585 Nyati 0.0225" 20.0 degrees
404 Jeffery 0.0420" ???? degrees
400 Whelen 0.0130" 17.5 degrees
400 WAI 0.0130" 40.0 degrees
10.75 X 68 0.0125" 20.5 degrees
458 IM 0.0225" 30.0 degrees
450 Rigby 0.0325" 45.0 degrees
475 Rigby 0.0175" 45.0 degrees
475 RI 0.0275" 45.0 degrees

I certainly think that a shoulder of (0.0300"/25 degrees) is a safe place to hang the hat. Thanks for your assistance.

Does anyone have the 404 Jeffery shoulder angle handy?

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RAB

[This message has been edited by R. A. Berry (edited 10-22-2001).]

470,
I did that,but I don't remember the results, sorry!!, but it is now a moot question now as Ricks is grinding a bigger hole in the back of the barrel.

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

RAB,

Upon further reflection (and remembering that the 505 Gibbs doesn't meet my previously stated preference) I would revise my recommendation to 0.025" with a 15 degree shoulder. I need to do this as I once owned a 505 Gibbs and never had any issues whatsoever. I will make some qualifing statements about this later however. Furthermore, I would recommend that with cartridges with minimal shoulder such I now recommend that only good brass is used.

There is something to be said about the physical diameter of the case shoulder and neck also. The setting back of the shoulder is due to extrusion of the brass from the force imposed upon it be the striker's impact upon the primer. Extrusion is a function of volume. As the percent volume increases the force required to extrude the volume increases. Therefore, with a truly large case like the Nyati while the shoulder is small the volume of that shoulder is actually quite large. Assumung that there is only a minimal amount of clearance between the case and the chamber I would not really expect to see the shoulder being set back unless: 1.) There is considerable clearance between the case and the chamber therefore reducing the effective volume of the shoulder. 2.) The striker force/travel was excessively high this would cause me to worry about pierced primers also. 3.) The brass was extremely soft such as 500Grains was describing in his comments on the 500 Jeffery thread.

Well if anyone really wants to get into the extrusion process let me know otherwise I will shut up for now.

Todd E

[This message has been edited by Todd E (edited 10-21-2001).]

This is an interesting topic, and one I've been wondering about myself.

The shoulder angle of the .404 Jeffery is 8.5 degrees.

[QUOTE]Originally posted by R. A. Berry:
Hi Ron,
Just to complete your list the measurements for the full length sized 470 Mbogo are shoulder dimension of .5725, the neck dimension with the bullet in place is .495 for .0775 difference. Dividing this by two leaves .038 per side at a 35 degree angle. Seems to fit all specs. The reamer specs are shoulder dimension of .5750, neck dimension of .505 and a 35 degree shoulder angle. 470 Mbogo

[This message has been edited by 470 Mbogo (edited 10-21-2001).]

FB,
Now I am really confused. Note that the G&A article has conflicting info in their drawing and the text, specifying respectively 15 and 30 degree shoulders for the 460 G&A, and they said the original 404 Jeffery shoulder angle was 30 degrees! What source did you get the 8.5 degree angle from?

redlegg155,
Are you out there? What was the specification for your 460 G&A. I don't have your reamer drawing handy at the moment, but will look it up later.

470 Mbogo,
Your cartridge is obviously well perfected.

Todd E,
I was kind of leaning toward the 0.025"/15 degree minimum too, but I am still confused about the shoulder angle thing. If that is good enough for the 505 Gibbs, then it is pretty good empirical evidence of sufficiency. Anything else about brass extrusion/compression under the firing pin blow is most interesting.

I am still wondering about the 8.5 to 30 degree spread on the 404 Jeffery shoulder?

It seems obvious that strong brass is desirable, of sufficient thickness and hardness, as well as uniformity in any way.

A larger diameter shoulder resisting deformation under the firing pin and thus making the borderline step down of the 585 Nyati less worrisome also makes sense.

A sharper shoulder (greater angle) would also seem to be more effective in preventing the swaging down under the firing pin, providing a more positive/definite headspace.

Some say the sharper shoulder doesn't feed as smoothly, but that seems to be a moot point when considering how well the 416 Rigby works with its broad 45 degree shoulder. It does have quite adequate body taper too, however.

------------------
RAB

I guess "it depends" is the best answer??? Like everything else in life, the absolute is hard to find. Relativity strikes again.

Relativity theory of wildcatting?

A rule of thumb: shoulder greater than 0.0250" step and angle greater than or equal to 15 degrees. Anything less and you are flirting with insufficiency, but, everything is relative:

Like the 404 Jeffery with its broad shoulder of 0.0420" and 8.5/??? degree shoulder?

Like the 585 Nyati with its minimal .0225" shoulder and slightly better than minimum shoulder angle of 20 degrees?

Ray,
What do you say the 404 Jeffery shoulder angle is?

------------------
RAB

RAB,

I did not put down a shoulder angle for the 404 Jeffery because I wasn't sure what exactly it is and would have to rely on memory. That said, two numbers bounced around in my head, they were/are 7.5 degrees and 8.5 degrees. I know though for a fact that the shoulder angle of a 404 Jeffery is no way near 30 degrees!

You were correct also regarding the effect of the shoulder angle. The steeper the angle the more it will resist extrusion. The 404 Jeffery's long sloping shoulder does extrude, but this is due to the much greater force attributed to burning powder not to a striker's blow (similar extrusion occurs with the 300 H&H & 375 H&H which I have personal experience with).

Ray, I know that you are a big 404 fan and that you load it up to over 2600 fps with 400 grainer. Do you get much cartridge stretch with those loads?

Todd E

[This message has been edited by Todd E (edited 10-22-2001).]

Yes the 404 has a shoulder angle of 8 degrees, 34 minutes.....

Yes, I get stretch out of the 2600 FPS loads but I get stretch out of the 2125 FPS loads with that 8 degree shoulder...Thats the price of owning a 404 Jefferys...Could have a special X die made and get around that now.

From an information standpoint the only powder for the 404 is IMR-4831..With a 400 gr. bullet, 95 grs. will get you 2653 FPS in a 26" tube and although near max is not a hard load on brass as I have loaded some of those cases as many as 8 times and have been using that load for years...I got it from an article written by Holt Boddington years ago..

By the same token you can get 2700 plus with a 400 gr. bullet in the 416 Rigby without much trouble...

These old cordite guns have a lot of room for powder and were underloaded for years after the cordite era, as they worked just fine at 2150 FPS.....

I like to load them at 2300 to 2400 for buffalo, thats more than enough and 2200 works just as well, which brings to mind that if you want more thump get a 458 cal. or 500......not more velocity inasmuch as big heavy animals are concerned...This doesn't apply to light skinned game where velocity is an absolute advantage in killing power....

------------------
Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

RAB....If tolerances are close enough,it probably won't matter in the real world but if tolerances are the least bit sloppy,I think that we're inviting murphy's law to play tricks on us when we allow case shoulders to get more and more diminuative.To use an analogy,we might be able to hang from a cliff by own fingertips but when trying to hang by our fingernails,we may be pushing our luck.

jagtip,
Agreed. But the big bore "DGR" ought to have a little slop in the chamber, shouldn't it? Hence, the minimum safe shoulder has some interest to it, doesn't it?

I wonder what Ken Howell would say about this?

------------------
RAB

RAB....I completely agree with that.I think your question has great merit.So if tolerances are kept generous for the sake of reliability,it seems that there should also be a reasonably pronounced shoulder,also for reliability.If either were to be strayed far from,it would seem to be a problem waiting to happen.....I only understand in a very general sort of way.I have no idea where the line is that shouldn't be crossed.The problem is that in order to find that line,we would have to cross it.And if we think we know where the line is,it may only work most of the time and most of the time is not good enough for a DGR.I would rather err on the side of caution.Sorry for rambling so long.

Gentlemen:
Maybe Ray can correct me, but when considering shoulder angle on any case you need to consider the way angles are measured. For instance, if you say, it is a 30 degree angle that may mean that it is an included angle. That is, the total angle is
30 degrees, on the other hand it can be a 15 degrees if you only consider one side. Let me see if I can give an example. If you machine something at a 45 degree angle the total angle is 90 degrees. If memory serves me the 416 rigby has a 41 degree shoulder. but it is only 20 1/2 degree per side. I hope this helps
George

[This message has been edited by George Hoffman (edited 10-24-2001).]

[This message has been edited by George Hoffman (edited 10-25-2001).]

RAB-
The 460 G&A has a 15* shoulder angle, which in itself is adequate. HOWEVER, the dimension that really matters is the amount of surface area on that shoulder. There isn't much.
I have went to the 450 Dakota for just that reason, it has more shoulder surface area and is much easier to load for. "Duds" are not what a hunter needs in this type rifle, and unless the loader is skilled and paying attention, he can create loads that have excess headspace in very short order. This cartridge is critical in that regard, IMO.
The 460 G&A needs a sharper angle to make it the "best" of the stoppers, IMO. I debated about having another reamer made with a 25* or 30* shoulder, plus dies, etc but in the end I made it easy and chose a larger case with sharper angle!

[This message has been edited by John S (edited 10-25-2001).]

Have we "found" a good reason to have a "belt" on a cartridge?

George,

The 416 and 450 Rigbys both have 45 degree shoulders per side if you extend the shoulders out they will intersect and form a 90 degree angle.

John S,

You statement is incorrect. The resistance to extrusion is a function of volume reduction. Surface area is only two thirds of it. The shoulder angle is very important as well. Not however from the perspective brass, but because it forms the lead in angle of the extrusion die i.e. the chamber itself. The more blunt (closer to 90 degrees) the shoulder angle the more resistance to extrusion. The vast majority of my extrusion experience is with steel so the following percent reductions in volume will be off. That said, when extruding steel your volume reductions must fall between 10 and 20 percent. If you have too low of a perncet volume reduction you will produce chevrons in the steel, if the percent volume reduction is too high you will buckle the bar. Now with cartridge brass the percent reductions will be different than those for steel. Also, the extrusion efficiency will be affected by the shoulder angle of the chamber (the higher the angle the lower the efficiency).

I will stop with the tyriad now, but still stick to my previously stated recommendations for shoulder diametral difference and minimum shoulder angle.

DB Bill,

H&H created the belt precisely because they did not trust the long gradual shoulder of the 375 H&H Mag case to resist the striker blow without extrusion. That said obviously a properly designed case will resist this force and perform well.

Todd E

Todd-
You are obviously much more skilled and schooled in all of this than myself. If I am on the wrong track then I stand corrected. However, I believe the G&A has both an inadequate amount of shoulder angle, and not enough area, which together cause a fine cartridge to be a commercial no-go. The dimensional variances of a factory produced chamber and commercially loaded ammo add up to unreliability in this case. This is precisely the reason Dakota chose to use the Rigby case for their 450, when all of their other rounds are made from the 404 parent, according to Art Alphin, who supposedly helped them in the design work of that family of cartridges.

John,

I was not attempting to slam you. Actually, if you look at my previous posts I agree with you 100%. I would hands down pick the 450 Dakota over the 450 Rigby or the 460 G&A.
To me the bigger the shoulder the better!.

Todd E

Well, I reckon the 450 Dakota is a humdinger. Adios 460 G&A, IMHO. Will anybody pay me 2 cents for that?

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RAB

Might give a penny! The 460 G&A is a great performing round and all one needs to do is start out with a better design. I believe Andy has such a rifle, called the 458/404imp. It should not suffer from the ills that plague the G&A. That said, the Dakota is still easier, and possibly better!

George Hoffman,
I think your angle explanation is why the G&A article showed a 15 degree angle in the drawing but referred to a 30 degree angle in the text. However, I have seen the 416 Rigby shoulder angle specified as 45 degrees per side, or 90 degrees total for both sides.

------------------
RAB

Moving this up for easier reference to the John Ricks continuation thread. HunterJim revived that one and some good scholarly stuff is starting to flow agaain on it.

------------------
RAB

I'm with DB Bill why not use the belt? If it is truly a life or death proposition are the belted cases shorter life expectancy that big of an issue?

Mike

Mike,
The belt only makes sense in special cases like the 375 H&H, 458 Win.Mag./Lott/Watts/Ackley, or 500 A-square, etc.

The 375 H&H needs the belt because of tapered case and weak shoulder, an inadequate shoulder.

With .510 caliber bullets, the A-Square ain't big enough for a beltless shoulder.

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RAB

Holy Cow! The 375 H&H has provided the answer again, as usual. Compare the cartridge dimensions below:

375 H&H:
shoulder angle = 12*45'
shoulder diameter = 0.448"
neck diameter = 0.404"
shoulder step = 0.044" total = 0.022" per side

460 G&A:
shoulder angle = 15*
shoulder diameter = 0.530"
neck diameter = 0.480"
shoulder step = 0.050" = 0.025" per side

I am now ready to hang my hat.

For a beltless cartridge of .375 bore or larger, shoulder angle MUST be greater than 12 degrees and 45 minutes per side. AND the shoulder step MUST be greater than 0.022" per side. To the nearest degree and thousandth of an inch thusly: 13*/0.022".

This is the "Thirteen-Twenty-Two Rule of Shoulder Inadequacy." Holland and Holland recognized it as an inadequate shoulder.

How much bigger in degrees and thousandths must one go for dud prevention in the beltless/rimless DGR?

The absolute answer is elusive because of variations in brass softness, firing pin impulse, increasing size of total shoulder area with bigger bores, etc.

If you have a much larger shoulder area as with the 404 Jeffery's Rimless Nitro Express,
you can make up for the angle with a bigger step: 9 degrees/0.035" per side.

Similarly the 585 Nyati makes up for borderline step with greater shoulder area generated by such a big case plus an adequate angle: 30 degrees/0.0225" per side.

This makes the 460 G&A (15 degrees/0.025") adequate but marginal, giving it the benefit of the larger shoulder area of the 404 parent case as compared to the 375 H&H based round (if it were beltless).

Reviewing all the readily factory loaded ammo it would seem that 30 degrees/0.030" per side is more than adequate for all bores and parent cases.

Rule #1: (13*/0.022") NOT adequate on the 375 H&H parent case (beltless).

Rule #2: (30*/0.030"): Totally ADEQUATE SHOULDER for any parent case (beltless) large or small.

Rule #3: In between and outside of these parameters, you pays your money and you takes your chances.

This is a synthesis of all the input of the members thus far on this topic. Thanks to all for allowing me to hang my hat somewhere.

When all is said and done, there are no absolutes, everything is relative, and it depends. That's life.

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RAB

Ron,

Thanks for synthesizing and posting your results! I was bumbling along with what I had, but I didn't have the dope on the .460 G&A. I have shot John Gannaway's rifle, and it is a nice one.

Maybe one of these days I will find a manufacturers rep to talk with and see what they think about "30/30"...jim

------------------
"if you are to busy to
hunt, you are too busy."

Jim,
Thank you for your thought provoking post on the other thread. Baie baie dankie.

I am going to retire from cartridge designing now, before I even got started.

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RAB

Thanks Dagga!

Mike

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Victory through superior firepower!

ready_on_the_right,
You are most welcome, and I speak for all the others, like HunterJim and Todd E that kept the ball rolling, I am sure. It may not be earth shaking but it is a place to hang your hat.

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RAB

I think some of you are missing the big picture...The G&A, the 404 Jefferys and almost all cartridges, including the 10.75x68 with good brass have plenty of shoulder and your not going to suffer misfires or headspace...Your being far to technical and living in a world of theory.

All these calibers have been doing marvelously for years, some for centurys without a hitch....

Best take into consideration which ones feed the best, such as the 460 G&A, 404 Jefferys..thats the ones your knocking..the only real world disadvantage is case stretching, if you consider that a disadvantage. I consider it part of the reloading agenda and a royal pain in the kazoo, but I can live with it until I get a set of custom RCBS X dies...

I shot the 400 whelen for years many moons past and never had a problem and it is an extreme case. I read all the hype about it but never experienced a problem with it and never met any user that did...

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Ray Atkinson

ray@atkinsonhunting.com
atkinsonhunting.com

Thank you for your opinion Ray!

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So many bovids! So little time and money!
RAB

sometimes these old threads are better than current ones...

the way the 10.75x68 getts lauded the 458 ruger min body taper will be o.k.

boom stick,
A blast from the past.

My latest thinking is that the chamber reamer shoulder must have at least 20 degrees and 20 thou per side, or I don't want to mess with it as far as wildcatting goes.

Just my "Twenty-Twenty Wildcat Shoulder Rule." Worth no more than my 2 cents.

Hindsight is twenty-twenty.

rip....i thought you would enjoy this thread again

20 thou is good and the 10.75x68 somehow works...