joining code 100 & code 83 - Model Railroader Magazine
If you are using Atlas products, the answer is so simple you'll laugh.
Just cut a deeper trough into the Code 83 ties, then slide an Atlas Universal Joiner (their standard rail joiner) onto the Code 100 rail, and push the Code 83 rail into the other end. No bent joiners, no soldering, no nothin'!!!
I lay my track with latex caulk, the railheads come out the same height, so all I did to assure there wouldn't be any unintended `step' at the joints was to put a flat surface (piece of plywood) over the joint area and weight it down with a full 2 liter soda bottle. Three years ago I laid one length of Code 83 in a Code 100 tangent as a test, and have yet to have any issues.
(I always knew there was some reason for keeping the soda we buy in case lots in the layout room...)
Chuck (Modeling Central Japan in September, 1964)