METALBALL2112
The area you need to fit is the rear tang (top surface) of the trigger that lifts up and contacts the safety selector core. We are not talking about very much, 0.001" to .003", typically (human hair is about .004" thick), pending on the stacking tolerances. A flat India stone to slowly take away .001" (keep it flat) at a time the top surface of the trigger until it clears the safety.
When you have aftermarket products like our safety selector and the Geissele triggers, we have all deviated from "Mil-Spec" or Mil Standards. This means not everything is going to be plug'n play every time. Our safety is designed to work with the MilSpec Trigger and many aftermarket triggers where the rear tang of the trigger bar is flat and parallel (both top and bottom) and typically machined to tolerance.
Fitting trigger to safety is not uncommon. You see that with JP Triggers (they even have a video instruction), AR Gold, etc.
The Geissele trigger rear tang top surface isn't flat, it is thicker than Mil-Spec and then it tapers down towards the end. It is not a machined surface but left as cast (as far as we know). With a normal 90 deg safety this is fine but with our 50 deg safety sometimes it will bind due to stacking tolerances. When we tested our safety with the Geissele Triggers they work fine but as we found out later that some will not work without some fitting.
We suspect it is due to the small amount of tolerance variance from the casting (normally +/-.005" for quality casting). Our safety selector centers normally will not vary very much since all surfaces are machined from billet bar stock on automated Swiss Screw Machines that holds easily +/-.0005" tolerance. Note that the issue can also be the relative positioning of the safety selector hole and trigger hole in the lower receiver and nothing to do with the trigger or the safety. The stacking tolerances between the holes can impact the trigger and safety engagement as well. The problem can
also be a stacking tolerance issue from a combination of all the above.
We have contacted Geissele about it and see if they would machine the rear top portion of the trigger rear tang to control tolerance so we can eliminate some of these stacking tolerance issues. We are still waiting to hear back.
Please note that we are not saying there is something wrong with the Geissele trigger or our product. Both products have deviated from Mil-Spec in order to innovate. When we do this, surface(s) that is not a critical tolerance or fell within acceptable tolerance when in combination with another Mil-Spec part can now be in conflict.
I hope that answers your question. If you're not happy with anything please give us a call on Monday when we re-open (9am-4pm PST) and we would be happy to take care of you and be sure you're 100% satisfied.
Thank you.