Either shooter induced bumping, or if you have a trigger over travel stop installed, you have it set too tight and the disco is not getting a good enough hammer retention to hold the hammer correctly at bolt lock up, before trigger release for hammer reset.

Without having the rig in hand to check it, Best to give Geissele a call to go over the problem and the needed solution.

Hammer down is just another way of saying hammer follow through, with either the disco not retaining the hammer as the carrier starts to move back forward, or you bumping the trigger forward when you fire the rifle for the hammer to be release and ride back down on the back of the carrier.

In regards to standard FCG, we re-time the Disco to a .001" to .003" free gap so it will not release the hammer until the trigger is dam near all the way back forward.  Not only does it prevent light trigger bumping since you have to take the trigger almost all the way forward before the disco will release the hammer, but cams the disco for more engagement of the hammer at retention as well.


With a two stage trigger, the disco is used for the second stage of the trigger, so its a mater of making sure that the trigger has enough over travel after the hammer is released so the primary sear has the correct amount of engagement to begin with , then the disco is set for the needed second stage increased weight tension.

Note, the way that the second stage works, the hammer is on the front primary sear, and as you pull the trigger, just before the front sear release the hammer, the back disco sear should make contact with the back hammer just above the sear edge.  The disco back sear increases the trigger pull weight, and if the disco is set up correctly, should the slightest of trigger pull past this way, release the hammer.  If the disco is set up too far cam back, you don't get the added weight before hammer release, while if the disco is set up cam'd too far forward, then you get the added weight, but end up with needed trigger pull creep before the hammer will release.

Also to point out, if you have over travel adjustments after the hammer has releases, do not set the over travel up like a bench rest gun, but instead add in around 1/4 more screw turn for a touch of excess over travel than you would on a bench gun.  What this does is allows the primary sear a touch more engagement to hold the hammer back when the bolt slams home and the hammer is not being retained by the disco.