I recently bought a Gen 5 Glock 47 MOS for a duty gun to replace my Glock 17 so I can put an optical sight on it.
I like to put a couple hundred rounds through a carry gun to make any problems show up and resolve them.
This one had an unusually hard trigger for a Glock.
I disassembled it and without the slide on the frame there was no problem.
I tried moving the firing pin and it took two men and a boy!
I removed the firing pin and checked for burrs and non were found so I put a drop of oil on it and reassembled the slide, there was improvement but still not right.
I installed the optical sight and went and sighted it in and the trigger was still not right so I completely disassembled the slide and found a burr on the safety plunger!
A couple of passes with a diamond file and reassembled and all is well!