Great for exo or endo mag builds - Cryptic 9mm PCC Bolt

I'm guessing the 1-star reviews are for Glock or Colt mag lowers. I built my AR-9 from a conventional AR upper and lower (Aero M4E1). The Mean Arms mags put the rounds almost directly in-line with the bore, so they chamber much more efficiently than the increased angle of pistol mags. You need the version with the ejector on the mag to work right, in this setup, but oh boy, does it! It even works with enhanced safeties (some mods to the weight required) ...ahem. Extremely smooth operation and cycling. Know that AR-9's are not Mil-spec and do your research on what applications the Cryptic works best with, and you won't be disappointed. The Kak K-spec heavy buffer for 9mm, and flat wire spring pair up well with this bolt, eliminating bolt bounce, and make a surprising soft recoil impulse.