According to the Wilkerson's book on Scouts, Peacemakers, and New Frontiers, The first 22 magnum cylinders were fluted. Most people are familiar with the unfluted 22 mag cylinders. Colt changed to the unfluted magnum cylinders so the owner could identify the magnum cylinder more easily.Not that I really know anything about the .22 mag, but I didn't know they made them fluted....mine is unfluted. Knowing that, I would love to find a fluted .22 mag cylinder myself....
That is the good thing about having the magnum barreled .22 peacemaker/new frontier. If a 22LR cylinder can be acquired then its no problem. sometimes the LR cylinder drops right in.. sometimes a little fitting is required, or it may not work if some gaps are too big. Colt went to 22LR only peacemakers/ New Frontiers in the 80's and it is not designed to shoot the magnum cartridge. Also as previously mentioned by Jerry, Some did come with only one cylinder in the 70's. These are rare and more collectible if the original box is with the gun so as the label can prove it came that way. (or Colt letter)My .22 Peacemaker is a 1976 vintage. I bought it from my dad a few years back and i doubt it had ever been fired more than a few times. It actually only had the magnum cylinder but was able to get a LR mag off a member here.