I recently purchased a Glock OEM +2 magazine extension for my new Glock 27 Gen4. Previous to installing the extension, I had fired around 500 rounds through the pistol with no problems using two stock magazines, and one magazine equip with a Pearce +0 extension. After installing the extension and a NY1 trigger spring, I took the pistol out to the range today. I fired 160 rounds through the weapon with two failures to feed. Everything except the extension and NY1 trigger spring are stock. I was shooting American Eagle FMJ 180gr, and with both FTFs I was shooting the gun strong hand only (I practiced with 50 rounds strong only; the other 110 rounds were with two hands or weak hand only). The FTFs happened two magazines apart; both times the FTFs happened around the third or fourth round (the magazines started fully loaded with one extra round in the chamber to simulate my planned carry mode, 11+1). With all of that out of the way: I think the FTFs may have been my fault. There were no FTFs when firing with two hands, neither was there any failures when shooting left handed. I haven't had a history of limp wrist with pistols, even subcompacts, and I have shot this Glock strong-hand only before with no problems. I plan to go back to the range soon, and I will get more results then. However, I wanted some opinions about what else could be causing the problem, so I know what I should be focusing on (other then making sure to grip the pistol better with my right hand). I have heard that aftermarket magazine extensions aren't a great idea; however I was shooting with a Glock OEM extension. I doubt that the NY1 trigger spring could have affected anything. Any words of wisdom, Glockers?