Originally Posted by rolyat
I assume there is heat applied to the bit of solder in the crimp barrel?
Yes, I'm talking about soldering the wire and terminal together after crimping. The solder has to enter from the terminal end and the amount of heat applied limited, to avoid having it wick down the wire and stiffening it, which will later cause the wire to break.
I'll also mention that I can't find any way to do this when splicing two wires together, as butt connectors are closed in the middle. I think it works fine to splice two wires by twisting them, and soldering- because a free hanging splice doesn't experience the same sort of cracking/bending torque that a flexible wire soldered to a fixed object does.
Perhaps another option would be to drill a small hole in the center of the butt connector and fill it in with solder. I haven't tried this yet.