Has anyone used the Calv Arms CAV-15 MKII lower receiver? It is a glass-filled nylon 6 polmyer receiver that has the stock (A2 design) and pistol grip attached. Fully compatable with MIL-SPEC parts. It retails from Brownells for $150.00, but needs lower parts kit and buffer and spring.
I would not use it with any upper over .223, but seems like it would make a cheap truck gun.