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There are a number of possible fixes for the poors who scavenge range brass or are gifted machinegun brass. Anneal first.I've tried all of the above, ultimately experiencing consistent defeat at the hands of bulk Lake City brass from God knows where.
I only bought LC .308 brass once, it was a total PITA - never again.
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!).
What the hell are you even asking?...anybody here have the proper background to explain this?
Bubbatechsaysos are not really helpful.
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.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...
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.
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.
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.No, you don’t really need Finite Element Analysis for this.
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
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.What I’m asking for is the property or set of properties that would explain such.
It isn't something that can be explained with simple classical equations, it really does require distributed methods…
Master's in Mechanical Engineering thesis by Ryan Stevenson: "Characterisation Study of Brass Cartridges for High End Competition Shooting," University of Strathclyde, 25/04/2014. I found it as a .pdf
While not explicitly stated - I wonder if initial cartridge size can be chalked in as “part geometry” influencing the final shape of pressed part.
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.
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.
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.”
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.
The dimension of the brass just above the rim that 1/8" or so that doesn't really get sized
You’re welcome?