My 19 gen 4 shots great. No FTF or FTE ever. It has the 0-4-3 reco spring that came in it but has a 336 ejector. Out of 100 rounds I get hit on top of the head ( not in the face ) about 3-4 times by brass. It isn't really a big deal as this is my carry a lot and shot a little gun. I called Glock and they said they would pay for shipping if I wanted to have the new ejector put in. I asked them to replace the extractor while they had it because we all know that's the real problem. He said they don't just replace those and they would put an ejector and send it back. If that didn't fix it then they would look at the extractor. So possibly two trips to fix it. If the gun functions and I trust it would you just keep it or send it back to try new parts???