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FULL LENGTH SIZING AND BRASS HYSTERESIS
- Thread starter Edsel
- Start date
The die mentioned above is kept at a setting for the bolt gun ONLY.
Measurements above are exaggerated for effect.
Just curious as to what measures you use to overcome this...
1. Number of "Compression Strokes"
2. Increased Dwell Time* in FLS Die
3. Better Annealing Practices
4. Increased Amount of Lubricant
I've tried all of the above, ultimately experiencing consistent defeat at the hands of bulk Lake City brass from God knows where.
Sooo much inconsistency with variable degrees of shoulder bump.
And they won’t chamber probably in the bolt gun unless I turned the die down some more.
* Side Note: Increased Dwell Time seems to yield the best results as far as consistency is concerned with "normal" brass.
Measurements above are exaggerated for effect.
Just curious as to what measures you use to overcome this...
1. Number of "Compression Strokes"
2. Increased Dwell Time* in FLS Die
3. Better Annealing Practices
4. Increased Amount of Lubricant
I've tried all of the above, ultimately experiencing consistent defeat at the hands of bulk Lake City brass from God knows where.
Sooo much inconsistency with variable degrees of shoulder bump.
And they won’t chamber probably in the bolt gun unless I turned the die down some more.
* Side Note: Increased Dwell Time seems to yield the best results as far as consistency is concerned with "normal" brass.
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You really can't expect to use the same die setting for multiple rifles. That setting is chamber specific, as the size of the brass being ejected is dependent on the headspace of that specific rifle. If you fire the range brass in your bolt gun once, and then resize with the die setup for the bolt gun, then the results should be roughly similar match your other brass.
There are a number of possible fixes for the poors who scavenge range brass or are gifted machinegun brass. Anneal first.
1. Try small base dies.
2. Try sizing first with a 30-06 small base body die, then size again with a 308 small base die.
3. Spend more money on a custom Warner Tool Company SAAMI minimum-dimensions die.
Good luck.
I know - it's an exercise in polishing turds.
Trash in, trash out.
But I'm trying my best to not just throw them out, and at least use them for plinking (bolt guns only!).
Better man than I then, I tried to work with them but eventually just dropped the 200 or so I had in the recycling bucket and went with new Starline.
The way to get better consistency from range brass is to sort bolt gun brass out. Auto rifle brass can be sized in several steps: Redding body die first, then FL die, then small base FL die. Each of these sizes the case a little more. Sizing effort is light.
If you don’t want to bother, then leave the brass in the ground.
If you don’t want to bother, then leave the brass in the ground.
Just a Bubba here, but remember this. In reality, you aren't just trying to push the bloated brass back 0.010". Its more than that, because the die is likely squeezing the body down by the base also, which lengthens the case. You're asking the die to do too much in one step.
All that brass has to flow somewhere when you size it, and it can only move so much per step without increasing the force to make that happen. Brass is elastic, so when the force required to move the brass exceeds what's applied by the die at the end of the stroke, it absorbs the last thousandths of movement like a spring. When you lower the ram, its springs back those thousandths. If you screw the die down further, the force to move the brass increases some and it sizes further, but push it too far and the brass will buckle, or kink, or deform somehow to relieve the pressure.
I think thats why @918v suggested leading with a body die, then doing full length to push the shoulder back some, and then going with small base dies to create brass that would be near factory size for use in whatever you wanted.
There are alot more knowledgeable guys on here than me, like Spife and 918v, so I'd love to be corrected if I have it wrong.
All that brass has to flow somewhere when you size it, and it can only move so much per step without increasing the force to make that happen. Brass is elastic, so when the force required to move the brass exceeds what's applied by the die at the end of the stroke, it absorbs the last thousandths of movement like a spring. When you lower the ram, its springs back those thousandths. If you screw the die down further, the force to move the brass increases some and it sizes further, but push it too far and the brass will buckle, or kink, or deform somehow to relieve the pressure.
I think thats why @918v suggested leading with a body die, then doing full length to push the shoulder back some, and then going with small base dies to create brass that would be near factory size for use in whatever you wanted.
There are alot more knowledgeable guys on here than me, like Spife and 918v, so I'd love to be corrected if I have it wrong.
Your foundation premise here in the above quote is misguided which is why you are having trouble if the goal in the end is to have correct sizing. There is a limit to materials like cartridge brass that is both strain and stress dependent, but there is still more to the story if you are trying to understand brass sizing to a fine degree.
Where and what ever gave you the idea that one die setting would work no matter the starting condition of the brass?
Stress and strain in metals like brass are not a beginner's topic, and it would take chapters in materials science and engineering to teach it. Then, simplified three term equations are for teaching first principals, but the methods to estimate this type of cold working on brass cartridges turn into finite element modeling for the kind of questions you are asking, so we won't even try to do this here.
But with that said, the expectation that a single die and setting can put cases back to size no matter what the starting condition of that brass is wrong, so you won't get satisfaction with a single die or single die setting.
Yes, I do get all that - don’t worry, all content is welcome
What I’m trying to do is get a proper explanation for said hysteresis - the observation that different sizes of brass, when sized multiple times against a smaller volume, will have different final volumes that are predicated by their respective initial volumes.
To draw an analogy, a 200 lb individual can only get down to 70 lbs after radical surgery, while a 120 lb individual can get down to 50 lbs after identical radical surgery.
The “limits” for each, if you will - are different.
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That would be extremely prejudiced and unbelievaly arrogant to make such an assumption.
No, you don’t really need Finite Element Analysis for this.
I already know how to get bloated brass down to the size that I want - you do eveeentually figure out how to, even through dumb luck or trial and error, after a few decades of mindless repetition.
But that really isn’t the question any more, is it?
I ask because maybe I have the background and education to do the math for all this and much more - but was not trained in this particular field.
Hence the introductory title of “Brass Hysteresis,” if that wasn’t leading in itself.
What I’m asking for is the property or set of properties that would explain such.
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Agree, you don't need analysis to size brass, but that is required if you want the reasons why it doesn't work the way you wanted it to.
This diagram that you lead with likely contributed to the faithful members of this forum not immediately recognizing you were looking for the mathematical derivation of modulus of elasticity
This diagram that you lead with likely contributed to the faithful members of this forum not immediately recognizing you were looking for the mathematical derivation of modulus of elasticity
I was hoping the plus - sized models would have been enough…
Thought they were trendy
It takes a study in finite element methods to explain the difference in sizing for reloading because there is a gradient of properties in a fired cartridge. The hardness or cold work state of the neck, shoulder, body, and head are not all the same.
To point you in the right direction, the concept of Modulus will eventually go from a simple stiffness term, to one that has a shear storage and shear modulus within it.
It isn't something that can be explained with simple classical equations, it really does require distributed methods to explain just the stress strain of reloading a fired case, and even more so when discussing the whole process starting from a "cup".
But we can make assumptions for simplicity, and purport that the shoulder and neck are homogenous for the purposes of explaining an infinitesimally small segment of brass springback, right?
We wouldn’t need to model the entire piece of brass.
Just read it - it’s an odd (poor) dissertation for an M.S. degree.
Just an observatonal study, doesn’t really discuss much, and doesn’t really touch on sizing…
…truth be told, I’m VERY surprised this passes off as an M.S. thesis.
I posted the question on a more relevant forum, let’s see if something comes up.
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Surprised to find probably 90% of the relevant discussion in simplified format here.
Woohoo!
While not explicitly stated - I wonder if initial cartridge size can be chalked in as “part geometry” influencing the final shape of pressed part.
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*** MIGRAINE TRIGGERED ***
This one’s a tough read but doable (handicaps of age and senility), probably not the best starting point as it has already diverged into a more specialized area, but covers all the key concepts.
Definitely no chest thumping or bloviating in this article
To reiterate - these are old, established concepts.
No FEA needed. The core principles are all there.
Apparently my initial search terms sucked - the proper gateway search terms leading down the rabbit hole are “FORMING” and “SPRINGBACK.” Not “HYSTERESIS” and “SOLIDS.”
All done. No more presuppositions or cut - and - pastes needed.
Apparently, it most definitely does (just reaffirming what we already inferred from bubbatech).
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From Stevenson 's (and others), every time a case is sized the case grows and the case walls thin. It was interesting to read firing has more of a work-hardening effect than sizing.“Springback Compensation Strategies.”
The spinning the case in a drill while holding to a torch flame (without a temperature or time standard) was rather ghetto.
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It is difficult to understand the problem here but I will give it a shot. The hardness of the brass can cause an issue and if you keep trying to size the same piece of brass over and over your work hardening it. The dimension of the brass just above the rim that 1/8" or so that doesn't really get sized can also be a big issue especially when shooting brass from another chamber. I only run brass that came from my bolt gun in my bolt gun.
With the information above - we got to confirm and put some pre - existing cocepts behind what we already know - you can’t slip into tight speedos if you’re morbidly obese.
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That depends on the die. If you match the dies to the brass or vice versa then that area really does get sized. That’s why it is good to have multiple dies cuz they often come in handy.
The easiest way to understand this problem is through friction. The bigger the case the more friction in the die. The more friction the less the brass conforms to the die. The less the brass can push into the die the more the stress on the press linkage. This in turn causes the die to pull away from the shell holder. The greater the space between the shell holder and the die, the less the shoulder gets bumped.
Spring back is a phenomenon that occurs when metals are bent, stretched or compressed and is the tendency of the metal to return to its original shape after forming. If the internal stress incurred in forming are less than the yield stress the material will return to its original shape. To assume a new shape the material must be stress beyond its yield point. It takes energy to achieve this as is obvious if you have ever tried to resized MG brass. The brass is forced into the shape of the die. When the case is removed from the die the case will spring back and release some of that energy as it tries to return to it original shape. The more the shape is changed the greater the spring back. The assumption that the case will assume the final shape/dimensions of the die is incorrect. The die must reduce the case below the final desired dimensions due to spring back. Spring back is also a function of time.
This is what happens on a macro scale. To understand what is happening on a micro scale would require a metallurgist to explain and I am not one. To the OP's original question to achieve the same final dimensions in the three cases with only one sizing operation the die will have to be adjusted differently and it may or may not be possible to get the same diametral dimensions with one die in that case.
When I size cases such as mixed LC that includes MG cases I will simply size the MG cases 2 or three times as opposed to once. I also never try to set the shoulder back only one or two thousandths in that case.
This is what happens on a macro scale. To understand what is happening on a micro scale would require a metallurgist to explain and I am not one. To the OP's original question to achieve the same final dimensions in the three cases with only one sizing operation the die will have to be adjusted differently and it may or may not be possible to get the same diametral dimensions with one die in that case.
When I size cases such as mixed LC that includes MG cases I will simply size the MG cases 2 or three times as opposed to once. I also never try to set the shoulder back only one or two thousandths in that case.
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The point of annealing is to stress-relieve the work-hardened neck and shoulders to reduce splits.
Here's a case diagram (lower left) that shows the hardness gradient of standard GI 5.56 brass. As the cases are drawn you want the head to be hard and the shoulders and necks softer.
For military use the case has to do its job once.
Here's a case diagram (lower left) that shows the hardness gradient of standard GI 5.56 brass. As the cases are drawn you want the head to be hard and the shoulders and necks softer.
For military use the case has to do its job once.
You’re welcome?
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