07-23-2012, 07:31 PM
The polymer ammo problems I am aware of came from heat resulting the rounds getting torn in half on extraction also if the were fired in a fluted chamber the just exploded, here is a list of the thermal conductivity of metals Aluminum is quite a bit more conductive than brass http://www.engineeringtoolbox.com/therma...d_858.html steel case is an option but I don't think steel cases would achieve the 10% reduction also upon further research aluminum is not a viable option as it was tried in the 60s apparently it's not safe over 40,000psi the had a problem with case burn through at least not in a cost effective alloy aparently the gau30mm uses aluminum cases but the gun was designed for them and the use a special aluminum alloy that is quite expensive