I will way in and maybe help . I bought an m&p 9 last year started shooting it in May with factory jacketed bullets shot fine and grouped good. Well I do reload like most of us do. 125 gr lead(missouri bullet) accuracy went to about 5 inch group at 20yds and had a lot of leading. I tried several different brands and coatings I didn't have as much leading with coated but still had some, accuracy wasn't good with any. I noticed that th bore on mine wasn't polished as well as my wife's m&p pro9 . I gave up and and bought an apex barrel and love it. From what I have read this is a sporadic problem with the m&p 9mm . I would recommend The Blue Bullet Company very good accuracy with these. Hope something in this rambling helps.