Sorry just saw this, but no, the ones we sell are aluminum. Armalite **may** have poly lowers but we have not been selling any of them. Regarding the previous comments about Rock River, Daniel Defense, etc.. those are all good brands and there are many more that I could have opined at length about but the OP had requested information about entry level rifles (less than $800).
I have built no less than 5 ARs. There are a ton of good tutorials out there. The only thing I would say is that there are a few tools that can make your life a LOT easier when assembling the lower... Castle Nut Wrench and the and the Pivot Pin Installation Tool.
