Decided to get back into Glock and purchased a new G17 Gen4. Aftyer everything I've read I was a bit nervous. I ran a test on 8 different 124gr ammo brands. I did the same for my HK P30L so I thought I'd try it on this new Glock. The born on date for this G17 is 3/24/12. I fired Winchester NATO, Lawman, Aguila, Fiocchi, American Eagle, Sellier & Bellot, Federal Premium Nyclad, and Speer Gold Dot +P. Again, there were all 124gr. Wanted to break the gun in using the Winchest NATO after a good Ballistol cleaning. Topped off all three mags with the Winchester and started shooting. The first magazine WAS A DISASTER. Every round would either jam, nosedive, FTE, FTF. I began to steadily curse louder and louder as I had to rack, tap, bang every round. Brass was either jammed in the slide or banging me in the face/head. I clearly remember thinking- "Call GLOCK RIGHT NOW". I was so disappointed thinking I got a lemon. Decided to continue and inserted the second mag of NATO afraid of what I'd find. To my surprise, everything went fine. I then shot 125 rounds of the NATO to break in the gun before shooting any other ammo. In fact, the next 40 magazines of all the various ammo fed & ejected just perfect. No brass to the head or face. Some was better than others but not a single issue at all. All ammo ejected to the right (although some more up and back to the right, but none to the head or face except for that first mag) Here was a breakdown: Winchest NATO- most definitely the most umphh of the group. These casing ejected much farther than any other. Lawman 124gr- No issue at all. Great ejection. Aguila 124gr- Very weak ejection. Powder flash present. Fiocchi 124gr- Short ejection, but no issues. American Eagle 124gr (this ammo was the weakest on my HK P30L, but did not notice that in the Glock?). Short ejection, but no issues. Sellier & Bellot 124gr- Very high ejection for some reason. All to the right but seemd to eject in a higher trajectory. Federal Nyclad 124gr- old ammo. No issue. Speer Gold Dot +P this ammo was ejected the second farthest (behind the NATO). No issues. One thing of note was that the last round of no matter the ammo always seemed to jump in a higher trajectory out of the gun. I gotta say that during the first magazine I was really aggravated. Had I not kept trying I would have given the doggone gun away. I am very happy with the performance on the Gen 4 G17 after that first mag. Maybe some of you experts out there can give some thoughts. I am guessing it just needed a mag to break in. Glad I had the NATO stuff handy. As I mentioned, I did run 40 magazines worth of ammo down the pipe (not all full 17 rounds, mostly 5-10 rounds). Got home and surprisingly the gun was no that dirty. When I field stripped the gun I somehow pulled the trigger housing out of the G17. I had NEVER removed anything like that before and was a bit concerned. I snapped it back in place and it seems fine. Hope ya'll enjoyed the ammo test and field report. Thoughts, comments, flames are welcomed.