Originally Posted By: bubbatime
From a safety standpoint, aluminum is safer in case of a kaboom. In an aluminum lower, it blows the magazine out the bottom and remains intact. In a polymer lower, the lower explodes and sends shrapnel into the shooters face - saw a case of that somewhere on the net.
The only real benefit of polymer is that it is lighter. If you plan on building an ultra light hunting or field AR that you carry a lot, then polymer might be a good choice. For an every day AR or a defensive firearm, I would stick with an aluminum lower.
I wouldn't want to depend on a polymer AR lower for anything I actually might want to use, like hunting or field use.
BSW