I'm not faulting what you did, just explaining what happened when you did it. Many aren't aware that when you change the point gap, you change the timing. That's why you gap points first, then set timing. Used points many times have pits in them so they need to be sanded or filed. Gapping used points with pits can only be done accurately using a dwell meter. The spark jumps between the pits and you can't measure that distance with a feeler gauge. The gap you set actually ends up being bigger. For this reason, used pitted points are best set to the lower side of the spec.