Brownells is making a somewhat copy of the AR-18/AR180 upper that mates up to an AR 15 lower but in 7075 aluminum. It does allow for a true folding stock with no buffer . Its basically what is SIG now using in its Virtus/Rattler MCX line for about half of what sig sells their upper conversion for . In any case the Brownells BRN180 upper comes in 10.5" and 16" for a pretty good price . I picked up a 10.5" and attached it to one of my SBR lowers. I also picked up a New Frontier side folding lower to put a fixed folder magpul A2 length stock on but until the stamp comes back it will be in this configuration.