I have bought 7 new magazines for my M&P 15-22, plus the one that came with my rifle. I have owned them and the rifle for less than three weeks and taken the rifle out twice. From the very first day out, I have had issues with the bolt not staying open after the last round is fired on occassion. Initially, I thought it was some kind of ammo issue. But, then I narrowed the problem down to just one magazine. The other seven allow the bolt to lock in the open position after they are emptied. After closely inspecting the offending magazine, I found that the follower is defective. The part that protrudes from the magazine is shorter than the other 7 that I own. I am enclosing a picture of the problem follower. I have swapped out the follower with ones from the other magazines and it works okay. Conversely, if I put the follower in one of the other magazines, the bolt will not stay locked back after the last round is fired. I have contacted S&W by email and I am hoping that they just send me a follower and not make me mail the magazine back.

Here's the pictures:

Email S&W, I bet they make it right, just gotta ask

You were right! They emailed me today and told me that they are sending me a new follower.

My mp 15-22 is the first Smith I've ever owned and from what I hear the customer service is the best in the biz.