The thread on the 5.7 varmint exterminator got me thinking. What about a 5.7 semi-auto carbine built along the lines of the M1 Carbine, simple blowback, and using FiveseveN pistol magazines? It would actually be an easier project to build a simple blowback rifle versus a tunbolt from scratch. You could use a lot of Carbine parts if you wanted to make it easy. Just spitballing here. Any thoughts?