I have not come across a post on how to tin barrels and ribs before putting them together.

Always under the impression that both surfaces had to be prepared first, it really set me back as it was:
-a big freaking mess
-I was concerned that I would overheat parts or cause other problems.

What I came up with was an "iron" that I could push down the rib/ inbetween the barrels that would tin both sides simultaneously.
Not too different from how they tin copper gutters.

All it consists of is a short(1") of round stock turned so that the edges contact the metal where you want the solder.

After turning the round stock to size, tin the entire piece.

Place it inbetween the barrels and direct the heat onto it

Feed in flux and solder on either side and progress down the barrel

It is helpful that it acts like a sink as well. On the shotgun tubes that I am working on it stays hot enough to melt solder on one side of the tube while anything on the other side stays attached.

I am sure that there are other methods and I would like to know what they are as well, shorter, more precise or just plain different.

Also, please chime in if I am making any mistakes.

Tom