After attending a 870 armorers course I found it funny how Remington specs its parts. Basically the part tolerances are factored as a whole and not by individual part. For instance if something is over spec they search for a under spec part to pair it with. No shit, this is what the Remington instructor was teaching on how to fix the gun. Has far as the trigger group goes they tell you not to attempt to fix it and send it to Remington. Was not impressed with the Remington armorers course.