IMX, the answer is - most likely. I have had few problems with a Mk I or Mk II cycling subsonic ammo as long as the ammo is slightly subsonic, i.e., around 1080 fps or there abouts. If the ammo is really subsonic such as Aguila Colibre, then the guns will usually not cycle properly. In fact the slide doesn't even budge. OTOH, it works fairly well with Rem. High Velocity .22 Shorts.
