Help! Spring barrel retaining ring is driving me insane!

[Couch Potato]

What I have found is that often the spring barrel is not round which makes getting the cover which is round back in very difficult and even more difficult to push in far enough to get the retaining ring back on. Solutions I have used: large clamps to gently try to bring the spring barrel back into round so assembly goes back more smoothly, on occassion have also employed multipule clams after that to push the cover back in far enough so that when the retaining ring is put is it fits back into the ridges from whence it came. Of course have also just clipped the retaining ring but that still won't make it seat properly unless the cover is down far enough.