Originally Posted by kayak
With or without the upper installed? The Geisselle hammer will hit the lower if the upper is not installed. Geisselle mentions that in the installation video on YouTube. Haven't had any problems with the hammer hitting anything it's not supposed to hit when the upper is installed.
I have some kind of error in the lower, the timney would not work, it would bind on the front of lower trigger housing (not milspec) which would bind up my bolt causing it to malfunction. The problem with the gieselle is it has a small raised portion on the front of the hammer which would contact causing light primer strikes. I remedied this by fileing this portion down until it did not hit. It now works great and is a 1/2 minute rifle.