I've got the Colt made Conversion Unit with the sliding chamber. It works on most Series 70 and earlier Colts that I've tried, but you have to keep that sliding chamber and the portion that fits into the bbl. proper, clean, clean, clean. Mine worked best with a light, very light skim of Rem oil or something equally thin. Accuracy was so-so compared with a Ciener, Marvel or Advantage Arms unit, however. Most ammo would do 2-3" at 25 yds from rest. Of the three 1911 units that I own, it's my least favorite for that reason. Good luck with yours. Rod