I like the Idea... but the practice doesnt hold to concept.
I think this could be a good bases for a 9MM SMG type unit - but as a .223 rifle - its a failure in my book.
The problem is that the polytype frame is just not stiff enough to support accurate rifle fire.
The reciever is the FOUNDATION from which you build accuracy. Bench Rest shooters often use custom made actions built like small Artilery batteries... Thick, heavy and nothing but solid. One of the reasons the AK is better than then SKS is it's a stiffer, heavier duty action. The Super VEPR - which is IMHO the best AK you can get - is based on the heavier machinegun reciever. This is all giving more support to the area supporting the barrel - the foundation...
We believe that polytype auto pistols may have a longer life span than steele - and have an easier "feel" when shooting because there is a slight flexation in the frame under the recoil stresses.
I suspect that in a rifle this slight flexation may throw off the barrel harmonics and increase barrel whip - possible causing the keyholeing, poor accuracy, and even screwing up its cycling.
Perhaps in a shorter 9mm configeration - these effects would be reduced... or just be unnoticed.
[This message has been edited by George Hill (edited April 18, 2000).]