Most mil-spec AR trigger pulls aren’t really the best they can be right out of the box. With a ceramic stone and a few minutes of time you can greatly improve the trigger pull of your AR15.
Following the instructions below, you should be able to make the trigger pull both smoother and a little lighter. If you are using ammo with hard military type primers you may want to skip the hammer spring bend I mention here. For commercially manufactured ammunition the spring bend shouldn’t affect reliability though. I only recommend the use of a ceramic stone as you can’t really over polish the sear engagement areas with this type of stone if you work slowly and carefully. Do not use any other type of stone or sandpaper.
As stated in the caption below, keep the sear engagement areas flat on the stone and as straight as possible. With a few passes you should be able to remove any minute burrs on the surface.
When you reassemble the hammer and trigger make sure the hammer legs are resting on top of the trigger pin and not underneath it. A little Moly Slide paste on the sear surfaces will make the trigger pull even slicker. Once it’s back together, perform a function test to make sure the safety and all the other parts are working properly.