Originally Posted By NAPOTS:
I spoke with Geissele this morning and the dimension for the hammer width is .690 +/- 3 so my receiver is tight. The tech I spoke with said this comes up fairly frequently so if anyone else runs into it, he said it is totally ok to file the hammer to make it fit. Its either that or hog out the lower with a dremel!
Do not hog out your lower receiver. It will be forever ruined. Always modify the less expensive, easily replaceable part. Do as the tech guy suggested, just lightly file or grind the sides of the bosses on the trigger or hammer until it fits down into your receiver and moves freely on the respective pin.