Dies for Bumping Shoulder

[pwc]

How has Guffy missed this?

[HiBC]

Don Fisher and 603 Country...If I understand you right I think you are partly right,with room to improve.

Don,I've owned and loaded for 3 7mm Rem Mags of my own..I understand and agree with the belted magnum case life issue you describe. I just don't 100 % agree with your solution. Belt headspacing was not designed around reloading.

It was designed around dangerous game. Its toleranced for reliability,once.

No one cares (but you) if yo only get 3 reloads. Because the belt is the designed headspace surface,additional clearance is designed in at the shoulder,and in the dies to be sure the belt remains the dominant factor in headspacing.
Its perfectly wonderful to choose to headspace on the shoulder! No problem! I do that myself!! We agree!!.

But here is a good,controlled way to do that. SAAMI won't help you,but you can use a "datum"ring bushing on the shoulder and a calipers to gain a comparative measurement of the fireformed case Yes? If you can do it for a 308,you can do it for a 7mm Rem.

Now,by the use of a feeler gauge or RCBS shell holders or trial and error or some secret salamander lips method,,you do NOT have to back the die off to partial resize,poke and hope,and let your shoulders be uncontrolled.
Why do that?

With some measurements and care,you can adjust your full length belted magnum resize die to full length resize,ignore the belt,and control the shoulder with the shoulder inside the sizing die to give you a known,controlled,repeatable .002 or whatever head clearance you want.

No problem.

We try to pass it on,no charge,you can do it too!

And we get the comeback " We been doing it this way and y'all are complicating it ….etc.

Thing is,I know exactly what I'm doing and the how and why.

Its really simple and easy. I'm just not worried about overcoming the resistance. I don't care if I convert you or not.

But I'll teach you for free.If you want.

[603Country]

I don’t reload belted cases, but you and I still appear to be doing the resize the same way. Your use of a “datum ring” is the more scientific and more accurate way to do it.

However, your statement that a fellow never has to back off the FL sizing die is not correct. It will depend on the size of the rifle chamber versus the resizing die. Maybe you just haven’t run into the problem yet.

[Bart B.]

With proper resizing, 20+ reloads per belted case is possible.

Belted cases originated at H & H to prevent rimless bottleneck cases with an 8 degree shoulder from shoulder setback from firing pin impact and feed reliable from box magazines. Original case was rimmed for double rifles then modified for bolt action rifles.

[RC20]

Belt headspacing was not designed around reloading.

Reality is the only system designed around reloading was a muzzle loader!

Cases if they do the job reliably once are the real mgf goal.

We luck out tht to meet that they do far better if we take care of them.

Rimmed cases are another case shoulder control (as we are not setting head-space we are jus making sure the case is loose enough to function which can mean +.003 or negative (-) .015)

[44 AMP]

Belt headspacing was not designed around reloading.

It was designed around dangerous game. Its toleranced for reliability,once.

This is a yes and no thing. There are few, if any rounds designed around reloading.

The first belted cartridge was introduced in 1912, the .375 H&H Magnum. H&H introduced the belted case and the term "Magnum" into firearms use at that time. This was done both as a marketing tool, and for a practical reason.

I don't know if it is accurate to say the belt was designed around dangerous game, but it was certainly first used there. The .375H&H does not have much of a shoulder. It was felt that the small shoulder of the .375 H&H case would not be enough for positive headspacing in "magazine rifles" (bolt actions) that were becoming popular at the time.

The belt allows for a positive "square shoulder" to headspace on, and avoids the issues of a rimmed case. It works tolerably well in both bolt actions and double rifles. Note that H&H also made the .375 Flanged Magnum, intended for use in double rifles, which had a case body identical to the belted magnum, but did not have a belt, it had a conventional rim, to be better suited to the double rifle extraction system.

The next belted round came in 1925, also from H&H, the .300 H&H Magnum. This case has a long sloping shoulder, again not well suited for headspacing.

For the next 30 some years, these were the only belted magnums, and the belt became firmly embedded in the buying public's mind as something "needed" for a magnum rifle case.

When Winchester created their line of magnums in the 50s and Remington did theirs in the 60s, "magnums" had belts, because that is what the public expected to see, and what they would buy. All those rounds were based on the original H&H case design, using the same head size and belt. Weatherby's Magnums began that way too, using "blown out" (less taper to the case bodies) H&H brass, necked to the bore size of interest (25, 27, .30,etc.)

Note that the later designed "ultra mags" and "short magnums" do not have belts. They feature very straight case bodies and large sharp shoulders which are easy to headspace on. Belts are not a necessity, they were something the buying public expected, at the time, and that's what they got.

As far as bumping the shoulder back a tiny bit, I understand the theoretical advantages, but not the practical ones, for me, or many shooters.

Certainly how much the brass gets worked during the firing and resizing cycle is a major factor in case life, but how much the shoulder gets moved during sizing is only ONE of the factors involved.

[Bart B.]

The reason competitive shooters full length sized belted cases bumping shoulders back a couple thousandths was to better center the case neck and bullet in the bore when fired. The belt never touched the chamber belt shoulder. Case shoulder centering in chamber shoulder was perfect when fired.

[RC20]

Certainly how much the brass gets worked during the firing and resizing cycle is a major factor in case life, but how much the shoulder gets moved during sizing is only ONE of the factors involved.

I have to heartily disagree. The normal push of following the die mgs instruction is what causes the case to crack above the base in short order.

That vastly supersedes any other factors that may or may not come into play in 20 or 30 resizing.

If those other factors are there I suspect the noise level is so low as to be totally irrelevant.

[HiBC]

Slightly off topic,but interesting.

Long ago ,maybe in "Rifle" or "Handloader" magazine,the topic of belts and the shallow shoulder angle came up.

I can't source this or back it up,but it seems like it could make sense.

A gentleman from England wrote in that Cordite was a factor.

According to his letter,they did not poke sticks of Cordite through the case neck in the loading process.The brass came as basic,cylindrical brass.

The charge of so many sticks of Cordite would be loaded in the primed basic brass,then the brass would be run through a case forming die to create the neck and shoulder. The shallow,gentle angles made case forming easier..But the shallow,gentle angles made for a lousy ,mushy,indefinite "anvil" to control for and aft location of the cartridge during ignition. The belt was a solution.

Its funny how a vestigial detail that is no longer relevant,like a belt,lingers on in tradition or market forces long after the initial reason ,(perhaps Cordite),has passed into history.

[Marco Califo]

Ah, Cordite. Amber strands, the length of the powder space. They did not use powder measures, but strand counts). I have a 303 somewhere and at one time had mil-surp 303 ammo, berdan primed. Might have been from India or Pakistan. I pulled a bullet and those strands could be coaxed out. It still shot.
Black powder (gunpowder is what UK called it) was replaced by Codite until WWII, when modern smokeless powders were invented. Both were used throughout WWII.
I believe one of the downfalls of Cordite was excess burn temp damaging MG barrels too quickly.
https://en.wikipedia.org/wiki/Cordite

[44 AMP]

I have to heartily disagree. The normal push of following the die mgs instruction is what causes the case to crack above the base in short order.

How do you define "short order"??

I think the important factors are the pressure of the load and the relationship in the tolerances of the rifle chamber and the sizing die.

High pressure loads simply "work" the brass more. A chamber on the large end of the spec and a sizer die on the small end work the brass more. The brass itself (and its previous life) matters.

I've got some .308 Win cases that I first loaded in the early 70s, dozens of firing loading cycles full length sized and fired out of the same bolt action hunting rifle, every time. NONE has failed. I got others, mil surp stuff originally fired in MG chambers that hasn't lasted nearly as along.

Have also had a complete head separation with a "once fired" commercial .303 Brit case, on its first reloading. When loading .303 Brit nowdays, I don't set the die to do more than the neck, if the case fits the chamber, otherwise. They still don't last long.

I won't, and can't speak to the importance of doing certain things for match shooting, I shoot milsurps and regular sporting rifles which often don't show any advantage using advanced match loading techniques.

[HiBC]

603 Country:

However, your statement that a fellow never has to back off the FL sizing die is not correct. It will depend on the size of the rifle chamber versus the resizing die. Maybe you just haven’t run into the problem yet.

I started handloading in the 1960's and barreling/chambering rifles in the 80's.

Fortunately,between my sense of workmanship and being taught properly,its true I have not run into many problems that were not easily solved.

Perhaps we only slightly misunderstand each other.

I assume maybe you have problems with your 220 Swift.Its a semi rimmed case,designed to headspace on the rim,with shallow shoulder angles and a tapered body. The Swift typically is being loaded with a 4000 fps + mindset.
My point is pressures are not likely to be mild.

It would not be unusual to have case life issues.

So far so good? We on the same page?

I can see no good reason to overly size the brass.I suspect your die is designed to get the case shoulder pushed down enough that the rim is fully responsible for headspacing. Often,the chamber is cut so that does not work out well. The solution,back the die off of the shellholder so the case headspaces on the shoulder. That's what I have done. I'm guessing we agree on that.

I'm thinking the only place we might be doing things differently is with "What is next?"

My understanding of "Partial sizing" is about backing the die off by "turns". One turn,or 1 1/2 turns,etc to just take the case body sizing out of the picture.
That's where we may part procedures. You might get away with using a Lee collet neck sizing die here,rather than backing your sizing die out to "partial size" I can't say for sure,I full length size.

But if I just wanted to headspace on the shoulder,without working the brass,I'd first measure the fireformed case,over the shoulder,by using a bushing. Just a ring to rest on the shoulder and give me something to measure. I'd screw my die down till I got a change of about .002 on my calipers after full length sizing.

Then,to make life easier,I'd try feeler gauges between the shellholder and the die to find one I could just put beteen the shellholder and die body,It might be the .008,I don't care.Whatever works. Next time,I screw the die down on the ,008 feeler gauge. So,yes,I would back the die off .008,but don't forget I sized that case for .002 setback,so my shoulder has been uniformy full length resized.

I use a gauge,not "Turns". Then I'd measure my results,because on tht day,with that brass,I might need a .010 feeler gauge or a .006.

And I am controlling .002 head clearance on a case shoulder that has been restored by the die to at least a degree.

In the handloading language I speak,that is still full length resizing.The shoulder gets sized,just far less. With the repeatable process,we have control,and can tune our outcome.

Calipers,a hardware store bushing,and some feeler gauges. It ain't a NASA project

And I'm happy to share . Good luck!

[603Country]

We appear to be doing exactly the same thing. As you guessed, when I spoke of backing off the die a bit, I was not talking turns of the die but more (which varies) parts of a turn. Because many folks consider that a FL resizing mean having the base of the die forcefully contact the shellholder, I started using the term “Partial FL Resizing”. But...then some folks thought I was talking about Partial Resizing, which I did for years and which worked great with the 220 Swift. After Partial Resizing, I went to neck sizing, then to neck sizing with the Lee Collet Die, then on to “Partial FL Resizing”. The Lee die worked great, but sooner or later the brass grows and has to be FL resized. And after a long series of tests I did with the 223 and varied methods of resizing, I found that the PFLR approach seemed as accurate as using the Lee Collet Die.

As for the 220 Swift, I’ve had this rifle since about 1980. Brass was hard to get, so I bought Norma factory ammo and reused the brass. It was Norma brass, and from what I’ve read (and believe to be true) that is some particularly tough and thick brass. It was originally a military round - the 6mm Lee Navy. I reloaded that stuff way more than I probably should have, but since I was Partial Resizing, it lasted for many years and a crazy amount of reloads. And the 220 brass does flow with firing, so don’t listen to anyone that might say otherwise. But, I didn’t know that back then, so I resized and trimmed and resized and trimmed, on and on. The consensus is that doing what I did with shooting and reloading that brass, with the brass flowing, the necks would thicken. They did not thicken. The neck walls actually thinned.

Anyway, regarding case resizing, we appear to be saying about the same things.

[RC20]

How do you define "short order"??

6 firing and 5 reloadings.

Go ahead and fire a case (lets use something common like 308/30-06/270) , measure the shoulder. Then do the die mfg contact the shell holder (assume no CoAx) and then turn the die in 1/4 turn.

Then measure the shoulder. Let me know what you get.

[HiBC]

RC20, I assume your comment was for someone else,,but I'll give it a try.

Who knows what mix of manufacturing tolerances you will run into,but the general plan is ,if we do as you say,we should produce ammo at the minimum

range of SAAMI spec,so it will work well in the tightest of SAAMI chambers.

But that is just what is "supposed" to happen. What you get is the result you measure.

I can't tell you what that will be,and neither can anyone else.

The tools SHOULD produce ammo that will work in any SAMMI spec chamber.

That will mean in many rifles,it will result in more than necessary head clearance. Excessive head clearance results in shorter case life.

With simple skills and tools we can set our dies to minimize head clearance to one specific rifle. That should extend brass life.

It seems so incredibly simple to grasp.I don't understand why folks have such a hard time with it.

What is so hard?

[Bart B.]

HiBC,

Some people cannot understand the mechanical interactions of case resizing in dies and firing in chambers. Some have shown good understanding and tried to convey it to the OP,

[HiBC]

Thank,Bart.

[HiBC]

RC 20,after reading your description of how cases fail...I havea different way of seeing it.
I'm not saying you are wrong,I just see it different.

For the purpose of this discussion,lets leave out headspacing on the extractor and out of spec firearms.

To close the bolt easily,we have some head clearance.Not a lot,but some. Agreed?

Some feature,whether it be rim,case mouth,belt,or shoulder,limits the head clearance going forward. The bolt face and lockup limit the rearward head clearance. Still good?

The firing pin whacks the primer.the case makes contact with whatever surface limits forward travel. The "Anvil".

The primer ignites the powder,and pressure within the case rises.

Still agree?

So,with the case forward,where is the thinnest brass,or,where does the brass begin expanding,obturating,to seal on the chamber first?

Its thinnest at the neck and the forward part of the case,like,right behind the shoulder.

And,it gets thicker farther to the rear, nearer the web. Still good?

As the pressure builds,the obturated case actually gets a good grip on the chamber walls. PO Ackley published his observations in "Handbook for Shooters." He took the locking bars out of a 94 Winchester and the brass bturation held the breech closed.

So,the thin walled brass is gripping the chamber wall. The barrel is not stretching. Everything is good . But wait!! We have head clearance and pressure is up there.The case stretches till the case head is supported by the bolt face. The chamber does not stretch,so the forward part of the brass has the friction to stay where it is.

Till you get back to that thick part of the brass,with not so much friction on the chamber,you know,right where the case fails. And that's where the brass case gets pulled like taffy. Its over a short length. Pressure keeps the brass against the chamber wall,and as the case stretches,it thins.Ever do the "Paper clip test"? You feel that stretch ring like an O ring groove.

Cut a case with a stretch ring and look.

It might be that very thin section will crack during resizing,but the stretch ring came during firing,not in the loading press.

And .005 or .007 head clearance can pull a deep stretch ring in 4 or 5 firings.

We do a lot better at .002. Much less stretch. Maybe we'll lose cases to split necks or loose pockets before that darn head separation happens!!

Anyway,thats how I see it.

[Bart B.]

^^^^^^^

Well said, very simple and correct

[Metal god]

RC 20,after reading your description of how cases fail...I havea different way of seeing it.
I'm not saying you are wrong,I just see it different.

For the purpose of this discussion,lets leave out headspacing on the extractor and out of spec firearms.

To close the bolt easily,we have some head clearance.Not a lot,but some. Agreed?

Some feature,whether it be rim,case mouth,belt,or shoulder,limits the head clearance going forward. The bolt face and lockup limit the rearward head clearance. Still good?

The firing pin whacks the primer.the case makes contact with whatever surface limits forward travel. The "Anvil".

The primer ignites the powder,and pressure within the case rises.

Still agree?

So,with the case forward,where is the thinnest brass,or,where does the brass begin expanding,obturating,to seal on the chamber first?

Its thinnest at the neck and the forward part of the case,like,right behind the shoulder.

And,it gets thicker farther to the rear, nearer the web. Still good?

As the pressure builds,the obturated case actually gets a good grip on the chamber walls. PO Ackley published his observations in "Handbook for Shooters." He took the locking bars out of a 94 Winchester and the brass bturation held the breech closed.

So,the thin walled brass is gripping the chamber wall. The barrel is not stretching. Everything is good . But wait!! We have head clearance and pressure is up there.The case stretches till the case head is supported by the bolt face. The chamber does not stretch,so the forward part of the brass has the friction to stay where it is.

Till you get back to that thick part of the brass,with not so much friction on the chamber,you know,right where the case fails. And that's where the brass case gets pulled like taffy. Its over a short length. Pressure keeps the brass against the chamber wall,and as the case stretches,it thins.Ever do the "Paper clip test"? You feel that stretch ring like an O ring groove.

Cut a case with a stretch ring and look.

It might be that very thin section will crack during resizing,but the stretch ring came during firing,not in the loading press.

And .005 or .007 head clearance can pull a deep stretch ring in 4 or 5 firings.

We do a lot better at .002. Much less stretch. Maybe we'll lose cases to split necks or loose pockets before that darn head separation happens!!

Anyway,thats how I see it.

I agree but how do the cases fail ? I don't see that in there , If the primary reason is not to much head clearance . What other normal part of case prep will cause case failures more often then to much head clearance over multiple loadings ?

Your explanation above and this below

I have to heartily disagree. The normal push of following the die mgs instruction is what causes the case to crack above the base in short order.

That vastly supersedes any other factors that may or may not come into play in 20 or 30 resizing.

If those other factors are there I suspect the noise level is so low as to be totally irrelevant.

is exactly how I got theses



To much headclearance over multiple loadings ( 3 ) is what caused my case failures . I had to much headclearance because I adjusted my dies as instructed by redding and has been the only time I've had case head separations .After learning how to adjust my FL sizing die to size a case to any specific rifle resulting in minimal head clearance I have not had another case head separation . So now I do all the other case prep stuff while minimally sizing my cases ( head to datum ) and have not even come close to another head separation . I conclude that " The normal push of following the die mgs instruction is what causes the case to crack above the base in short order. " which is screwing down the FL sizing die until it makes contact with a/the standard shell holder then an extra 1/4 turn or so . Is by far more likely to cause case failure over multiple loading then ANY other one thing in case prep . Agreed ?

So in conclusion I agree with both quotes .

[T. O'Heir]

"...I am "bumping" the shoulder back..." No you're not. You're resizing the case back to SAAMI spec. Cases DO NOT have head space. Headspace is a rifle manufacturing tolerance ONLY.
"...headspace on a rimless bottleneck chamber gauge?..." Nothing. There's no bolt face.

[HiBC]

Those are stretch rings gone to the point of breaking through.Saw them lengthwise. You might discover them at the press,but the damage was done upstream .

If you prefer not to click links,go to Varmint Al's Website.

On the left column,select the article on "Chamber finish"

If you scroll roughly halfway down,there will be a finite element analysis cartoon labeled "rough chamber finish" and "friction co-efficient 56

Watch the cartoon and you will see how the stretch happens,

http://www.varmintal.com/a243z.htm

[HiBC]

To much headclearance over multiple loadings ( 3 ) is what caused my case failures . I had to much headclearance because I adjusted my dies as instructed by redding and has been the only time I've had case head separations .After learning how to adjust my FL sizing die to size a case to any specific rifle resulting in minimal head clearance I have not had another case head separation . So now I do all the other case prep stuff while minimally sizing my cases ( head to datum ) and have not even come close to another head separation . I conclude that " The normal push of following the die mgs instruction is what causes the case to crack above the base in short order. " which is screwing down the FL sizing die until it makes contact with a/the standard shell holder then an extra 1/4 turn or so . Is by far more likely to cause case failure over multiple loading then ANY other one thing in case prep . Agreed ?

Bingo.

And you discovered the important part. If you are reloading for 9 rifles of the same cartridge,the rifles have tolerances. So,you follow the die mfgr;s instructions. You will get minimal dimension ammo,which will work in all the rifles (probably). But you will also have excessive head clearance with some rifles,and case life will suffer.

OR,you may handload ammo with controlled minimal head clearance for one rifle,and get maximum brass life.

This ability/flexibility is part of what advanced handloading is all about.

You got it!!!

[Unclenick]

Originally Posted by HiBC

Watch the cartoon and you will see how the stretch happens,

Actually not a cartoon (artist-drawn animation). Those animations are computer output from a fancy government finite element modeling software package that is actually analyzing the interactions of the material specifications and their properties in response to pressure rises put into the software as arguments. The software output has an option to exaggerate the bends and distortions caused so they are more visible to a human observer. The rainbow colors show the stress locations and degrees calculated by the softward. It's a pretty nifty tool.

[HiBC]

"...I am "bumping" the shoulder back..." No you're not. You're resizing the case back to SAAMI spec. Cases DO NOT have head space. Headspace is a rifle manufacturing tolerance ONLY.
"...headspace on a rimless bottleneck chamber gauge?..." Nothing. There's no bolt face.

I'm not the police. You can write anything you want.

But please review this thread. Read the posts. See how much dialogue...pleasantdialogue,we have had,and the amount of information that has been exchanged.

And we did it without the same old tired arguments. We are communicating.

Its been nice.

I've been reasonably careful to keep my writing technically correct.Let me know if you have specific complaints.

But what I'm NOT going to do is nit pick somebody else who is making an honest attempt to learn,understand,and contribute.

Once foks understand the concepts,they can fine tune the terminology over time.

If you assign a first grader to write a story about the weekend,and the first grader writes

We wnt tu the crcus and saw a elfunt.

You read it aloud with delight! You went to the circus and saw an elephant.

You let the kid be excited with success!. Communicating. We got his idea!

Let reading and writing be enjoyable.

Don't crush him with phonics,spelling,punctuation,yet. He'll get that...maybe if you just let him enjoy reading books! What better way to learn to spell?