Quote:
Originally Posted by 5-Shot
Correct me if I'm wrong, but I thought all IMR type powders did have the same chemical composition. (And yes, I understand that the ballistics part of this discussion would devolve into integral calculus. I'm asking a much simpler question.)
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Good point, depending on how approximate an answer you're willing to accept, and for what purpose.
Roughly 15% of the weight of an IMR powder is not the actual powder but coatings, graphite, etc that participate in the combustion, and their amounts and types vary. Also the pressure during combustion will affect how much of the powder actually reacts, and how much unburned remains.
So if "about X cc after complete combustion, at standard temp and pressure" is good enough purely as a matter of interest, then sure, why not? I would tend to change the 20.54 ci to "about 20" and leave it at that.
Obviously the volume of the gas when the bullet leaves the barrel is going to be the volume of the barrel and case, at a much higher pressure and temp.