This is going to be a long post, so please bear with me. I recently purchased a Gen4 G19 which came with an 0-4-1 recoil spring assembly. And during my first range outing, out of 300 rounds, I experienced three stovepipes and a significant amount of brass to the face, erratic ejection, especially with 115gr Remington UMC. Rather than send the pistol back to the factory, I decided to troubleshoot it myself. I recently took interest in some posts I'd read suggesting that the newer extractors might be the culprit in at least some Gen4 9mm issues. Specifically, member "HotroderX" mentioned Lone Wolf's extractors which promised better fit and finish over the more recent Glock extractors, which some speculate are MIM. After speaking with Glock customer service yesterday, he recommended I take some fine steel wool to my Gen4 extractor to smooth out the finish a bit and see if that would improve the fit. I did as he suggested, but during the process, received my Lone Wolf 9mm extractor. While the steel wool DID improve the fit of the Gen4 extractor, I noticed some small, yet OBVIOUS differences between the Lone Wolf version and the Glock version. In fact, the Lone Wolf extractor looked and fit EXACTLY like the extractor in my older Gen3 G19. The Gen4 Glock extractor has the obvious dip that others have mentioned as well as some extra ridges that don't exist on the older Gen3 extractor and the Lone Wolf version. So today I went to the range to experiment. Here are my findings... 1. I fired 400 rounds total. A mixture of 115gr Blazer aluminum case ammo, 115gr Federal American Eagle, 124gr American Eagle and 115gr Remington UMC (which resulted in 3 stovepipes and the highest amount of brass to the face during my range outing last week). 2. My gun came with the 0-4-1 RSA. I received my 04 spring today from Glockparts. I observed that the plastic on the muzzle end of the guide rod on the 0-4-1 version is beefier than on the 04 version. NO noticeable difference in performance. 3. The stock extractor performed much better this time. Which is to say I had ZERO stovepipes, FTF's or FTE's. No malfunctions whatsoever. The brass to the face was significantly reduced, but still occured from time to time, which seemed to only occur with the Remington UMC ammo. I cannot say whether it was the steel wool rub down or the break in from last week's range session that helped. 4. The Lone Wolf extractor performed brilliantly. NO malfunctions at all and NO brass to the face, even with the 115gr Remington UMC. 5. Again, there was no noticeable difference in performance/feel between the 0-4-1 and 04 recoil spring assemblies. Both proved 100% reliable. 6. I just got off the phone with an old timer at Glock customer service who I've dealt with before. He's a great guy who will remain nameless here per his request. He was VERY interested in my findings and thanked me repeatedly for sharing this all with him. I expressed to him that whatever changes GLOCK has made to its extractors in the past year or so should be looked at as a very likely culprit to the issues that some folks are having with their 9mm Gen4 pistols. I told him about the obvious physical differences between the newer extractors and the older ones and how Lone Wolf's design mirrors the older Glock version in fit, finish and function. He was very interested in this and suggested he would contact Lone Wolf for a comparison. I hope his findings will raise some eyebrows in Austria. 7. Since my experiment didn't even come close to properly following the scientific method, I can't positively say why the pistol performed so well today compared to last week. It may have simply needed some break-in, either the extractor, the recoil spring, or both. Perhaps the steel wool rub down did actually make a bit of a difference. That all said, the Lone Wolf extractor performed the best and it will stay in my gun along with the 0-4-1 spring. The 04 spring will go in my spare parts box. 8. Finally, I am more than happy with my Gen4 G19. Through 400 rounds of various types/grains, today it performed as a Glock should, especially with the Lone Wolf extractor! I suspect an older Glock extractor would have given equally excellent results, but I didn't think to take one along with me. I would not hesitate to recommend a Gen4 G19 to anyone who's on the fence. If yours is not totally dependable, try an older extractor or one from Lone Wolf and I'm certain you'll be good to go. -- Also, thanks to HotRoderX (and others) for their posts regarding the extractor differences and the Lone Wolf part. I found them very helpful. THIS is how problems get resolved. I believe consumers are a vital link in helping companies improve their products and resolve problems as they arise as nothing is ever truly perfect. Collaboration and problem solving are always more helpful than just whining and belly-aching.