Anyone familiar with Kurt Wala's work on custom AR's? KKF offers the P109, an AR with a .357 SIG upper, using modified Sten or Uzi mags. The feed is reliable and the cartridge achieves 1600-1700fps from a 16" barrel. I've heard anecdotal reports of up to 1850fps, but haven't seen independent confirmation of that. In tests, FMJ defeated Level II, and JHP was barely stopped by Level II and still inflicted significant damage.
I've been wishing for a pistol caliber carbine to complement what I carry, and I'm giving this one serious consideration. Any thoughts?