--ol' Dan_Oz is omitting the fact some brass doesn't spring back as much and all brass loses a tiny bit of it's elasticity every time we fire it.
I omitted saying that because it is arrant nonsense. I covered this earlier in the thread.
But it's not arrant nonsense any metal including brass work hardens. And it doesn't matter if we squeeze it a lot with a die and lose a lot of elasticity or expand it a little with chamber pressure and lose a tiny amount each time.
I understand the difference between ductility and elasticity.
Although you may be correct a neck die can potentially pull the neck forward--which is why I lube the necks of my brass even when the neck die doesn't call for it. It's easy enough to measure if that happens with my Stony Point gauge.
Casey, what do you exactly mean by "losing" elasticity? I guess in 30+ years in the materials testing arena and having tested all sorts of engineering alloys, I'm curious to what you mean by "lose". I gather that Dan has a materials background and understands strain hardening, strain softening, elastic-perfectly plastic, Ramberg-Osgood, elastic unloading, consumed ductility, etc. and this may be his refined understanding of material mechanics.
Elasticity is the Hookean response of the material..ie the linear stress-strain response. To say a material "loses" that means it's modulus changes over strain cycling; which is absolutely not tne case for cartridge brass or a wide range of engineering alloys. Its proportional limit/yield strength (increases for strain hardening materials) will change assuming plasticity is reached and ductility is consumed. Subsequent plastic strain cycles will have a new characteristic stress-strain response if plasticity has been reached during previous cycles but its elasticity (linear response) will not change or be lost. The unloading stifness would clearly show that.
JF
