Colt first recognized this in the 1960s, and produced a polymer version of the M16 which integrated the buffer tube and stock, along with the receiver in an attempt to address this shortcoming, but it never went in to full production as they already had the tooling set up to make Stoner’s design in alloy. KE Arms STRIPPED KP-15 LOWER RECEIVERS POLYMER $109.99 at Brownells KE Arms STRIPPED KP-15 LOWER RECEIVERS POLYMER $109.99 at Brownells