I found the thread with Parashooter's diagram:    (You need to Login
To find it I went to yahoo and typed this into the search line:
  krag collectors association rim lock echelon
Google is actually more powerful but yahoo allows opens another window for you to look at, close it if it is wrong and type another search phrase.
You have eliminated something wonky happening with the ejector, correct?
In my short experiment trying to get a rim lock the speed which the loading gate and which way the gun was aimed while closing the gate made a difference. Maybe some experimenting is in order to find the solution.

My apologies I was at the end of page one and did not realize Parashooter had copied his diagram in to this thread when I posted yesterday. Instead of deleting this post I will leave it as some other useful info is in the other thread.