Spent case necks getting dented from the ejection process is pretty common. If it's not too bad, the dent is removed in the sizing step. If it's kind of bad, then the neck might have to be straightened a bit before sizing. If it's mangled, then most just toss the case. The thing that confuses me about the OP's question is that he talks about the case neck firing forming in the chamber. That would make sense for the body or shoulder, but not a neck. It should always be in a cylindrical shape after sizing.
Last edited by Bret; 08-31-21 at 13:29.
Can you link to me somewhere that explains how burn rate has a significant increase as pressure rises? That seems backwards. I’ve been under the impression that burn rate remains relatively stable, but temperature has a direct relationship with burn rate, thus increasing pressure all things being equal.
The way you’re explaining it, it would be an exponential relationship as higher burn rate equals higher pressure which equals higher burn rate.
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I can't find anything authoritative offhand. I found this forum post (yeah, who knows) saying the same thing:
https://www.bullseyeforum.net/t2279-...uivalent-chart
The problem with burn rate charts is that they are speculative, or in other words, educated guesses. None of these charts are arrived at by testing each powder in the same application to determine how they line up in terms of burn rate. A characteristic of smokeless powder is that as the pressure goes up, the burn rate increases disproportionately faster. This is why you can get to a point where the pressures spike with small charge wt increases. The chemical makeup of a powder can determine how fast the burn speed increases as the pressure goes up. Some powders increase faster or slower than others. This simply means that you can make some general assumptions by looking at burn rate charts. However, just because a powder is located at the same level as another on the chart does not mean that these two powders are indeed the same, nor does it indicate these powders will react the same in different pressure ranges.
Under the ideal gas law, in a confined space more temperature creates more pressure, and more pressure creates higher temperatures. So while I can't find another direct statement that the burn rates accelerate with pressure, it seems to follow from basic gas physics. There are various statements that double-base propellants (containing nitroglycerin) burn faster at higher temperatures.
https://infogalactic.com/info/Ideal_gas_law
I believe it is. Search for Vieille's Law.
https://www.nakka-rocketry.net/burnrate.html
https://bisonballistics.com/QuickLOAD.pdf (page 97)
http://www.wydawnictwa.ipo.waw.pl/ce.../Boulkadid.pdf
Last edited by Disciple; 09-03-21 at 13:15.
Reading through, how would Saint Robert’s law apply? And the N value would determine to what degree burn rate increases, am I understanding that right? And the closer to zero the N value is, the effect would be less.
Where I’m struggling to apply it to gun powders used on most modern cartridges, velocity would likely decrease as charge and pressure increase on larger cartridges.
Perhaps pressure never gets high enough for the phenomenon to exist on rounds we commonly shoot. I don’t know, more or less thinking out loud. It’s an interesting subject.
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