SIG Sauer had this nifty short barrelled SIG 516 on display at AUSA ’12. I hope this design (with or without the short barrel) goes on sale to the public.
So many companies have developed compact AR stocks but are reluctant to sell them to consumers. One example would be the nifty stock featured on the Colt Sub-Compact Weapon (SCW). The SCW never went into production and the stock design never went on sale to consumers.
[ Many thanks to Lionel for the photos. ]