I have experienced perhaps three FTEs over the first 1200 rounds with a factory recoil spring with my Pro. As posted earlier, I experienced five FTEs during a total of ten stages since going to a 13# recoil spring. Since polishing the chamber, I shot a four stage match and experienced one FTE. A local gunsmith, commented that he thought the extractor seemed to have adequate tension. He also explained to me that after detonation, the cartridge expands to seal the chamber and then contracts. He suggested the barrel could be unlocking before the case contracts, causing the ejector claw to pull over the rim and leaving the case still in the chamber. I understand that the recoil spring affects the timing of the unlocking of the barrel. If this is correct, would a stronger recoil spring tend to delay the unlocking of the barrel, and thus increase certainty of ejection? What other factors affect the unlocking of the barrel? Barrel fit? Thanks for any comments. I really like the M&P Pro. I really would like to get it 100%.