8 round mag - Smith & Wesson S&w Magazine M&p9 Shield Plus 10 Round Black

10 Round Mag? More like an 8 Rounder! I can only put 8 rounds into the magazine because it’s stiff! I even took the magazine apart to loosen up the spring, put it back together and still can’t get that 9th round in! Kept putting in and taking out the rounds to loosen it also, nothing. I left the 8 rounds in for over a month to see if it’ll loosen as well, still nothing