American Tactical Alpha Maxx 5.56 7.5" Barrel 60-Round - $319.99 + Free Shipping

As cool as these look, and the low price is very tempting, do not be fooled that these can hold a candle to an all aluminum and steel rifle. Unless your just looking for a safe queen to take out once a year to shoot a few rounds, I'd suggest you understand the limitations and reliability of an all polymer gun.
I don't care what anyone says, polymer IS going to warp and crack over time on any gun that's actually used frequently. The manufacturers have had to add layers of steel over the years to keep the guns somewhat together. Heating, cooling, high pressures, and even weather is going to cause the polymer to shrink, expand and warp at some point causing failures. Then as if the polymer uppers and lowers aren't enough, these use plastic triggers and internal components.... Add all this up and your shooting a ticking time bomb... Ok maybe not in the literal sense, but close. Spend another $25-$75 and get an all aluminum pistol or rifle from PSA, BCA, Anderson, etc etc...There's plenty of aftermarket parts like carbon fiber handguards and minimalist stocks and braces to reduce the weight if that's what your trying to accomplish.