So as not to derail FortTom's thread, I'm starting a new one. That thread may have solved a conundrum for me - what to do with the "spare" upper I have? I'm now thinking a Faxon 16" "Gunner" barrel in 7.62x39 would add ammo capability and keep a familiar platform, plus I already have plenty of furniture and parts so I wouldn't be starting over from scratch. Does anyone have some personal experience or good links on building such an upper? M4 ramps versus something else? Any issues with using the Vltor A5 buffer system, mid-length vs. Carbine gas, etc.? Magazine recommendations also - apparently Magpul doesn't make AR mags in 7.62x39, so I'm at a loss as to what a decent brand would be.