I have had a tricky problem inserting a DB type mainspring into the barrel of an IWC cal 83. The tang of the outer mainspring bridle must fit into the tiny slot at the base of the barrel.     When the mainspring is pushed from the winder onto the barrel, despite all attempts to line up the tang with the slot it invariable ends up with the tang way outside the slot. With the mainspring fully unwound  nothing will shift the position of the bridle. My solution is to clamp the barrel into a De