I have a M9-A1, latest gen with roller pin. According to its production code it was manufactured April 2012. It has somewhere between 500-600 rounds through it.I noticed one day after cleaning that it had an issue with resetting the trigger. It would reset if cycled slowly, but not if I racked it back hard and let it it slam home. I followed Big Taco's reset tutorial and after I disassembled it, I noticed that the flat part of the trigger bar that engages the sear visibly greater than 90 degrees. Using the appropriate tools, I bent the flat enough to line up with a precision square. I disassembled the sear assembly as well just to check things out and give everything a good scrubbing. I reassembled everything following the Sear Mechanism tutorial to a T. The problem now though is that I can not rack the slide without pulling the trigger if the firing pin is de-cocked. Once the firing pin is cocked I can rack it all day without having to pull the trigger. So I then put the slide on the subframe without the plastic frame to take a closer look at what was going on. This is what I saw happening.
With the firing pin de-cocked, the flat vertical part of the firing post is in front of the sear. When I try to rack the slide, the post starts to push the sear assembly towards the rear. This is when the hooked part of the drop safety is around the trigger bar and presses it up against the under side of the sear and everything binds up. The slide won't budge beyond a slight initial travel. I have done a couple tests to make sure this is the problem. First I put everything back together minus the drop safety and I can rack the slide without holding the trigger. Then I reassembled it with all parts with the trigger bar out of the sear area and it can be racked without holding the trigger.
I hope I explained my issue well enough. Any thoughts or suggestions? I would like to try to repair on my own if possible. Thanks.