I have an M&P 9mm full size that I bought in May and has almost 6,000 rounds through it. Stock except for Apex DCEAK installed in October. Just recently experienced a severe loss of accuracy with the pistol. It was never as accurate as I would have liked, but was accurate enough. It also always shot better with 147 grain bullets. I noticed over about the last two weeks my scores on some drills getting worse. Then a shot an informal match last week that included a stage with steel plates out to 20 yards. I could not hit the plates! After the match I borrowed a pistol from another guy (Springfield XD) and hit the 20 yard plates every time. So I went to the range Wednesday night with a box of American Eagle 115 grain and shot from a sandbag rest at 25 yards. 10 shots fired and only 4 holes in the target (8 ½ x 11 paper). I borrowed a range Glock 17 and shot about a 3-4” group with the same ammo. Then I got out my carry ammo (Winchester Ranger-T 147 grain) and tried it. 2” group with the Glock, 7 hits scattered around the paper with the M&P. All the holes are round, no keyholing but no discernible grouping. As near as I can tell the pattern is centered, not noticeably high so I don’t think it the early unlocking problem some have had.
I took the gun apart at home and cannot find any obvious cause, no unusual wear or damage. Called Smith & Wesson yesterday and they are sending a shipping label to return the gun. Any of you guys have a guess as to the cause or seen something like this before? The fact that it was shooting fine and the accuracy suddenly went away seems to indicate something broke or suddenly wore out but the barrel, slide, and locking block look fine. I will update when I get the gun back from S&W and find out what they say, but I wanted to put the info out there and see if anyone else has had this happen.