07-23-2012, 02:19 PM
Per a number of discussions I've seen, one of the deterrents to using polymer or aluminum as substitutes is heat.
[INDENT]Full auto fire heats the barrel and the chamber a LOT!
Polymers tend to get unhappy with the higher temperatures.
Aluminum is a better heat conductor than brass, so cook-off becomes a problem.
Both of these issues become evident when a live round is left in the chamber after a magazine or so is expended on full auto.[/INDENT]
My hiccup with that summary is that very little quantitative information is offered to support the observations. For example, how long does a cartridge made from each of the candidate materials survive in a chamber with a temperature of 250F? 350F? 450F?
How significant are the differences? etc.
[INDENT]Full auto fire heats the barrel and the chamber a LOT!
Polymers tend to get unhappy with the higher temperatures.
Aluminum is a better heat conductor than brass, so cook-off becomes a problem.
Both of these issues become evident when a live round is left in the chamber after a magazine or so is expended on full auto.[/INDENT]
My hiccup with that summary is that very little quantitative information is offered to support the observations. For example, how long does a cartridge made from each of the candidate materials survive in a chamber with a temperature of 250F? 350F? 450F?
How significant are the differences? etc.