I've got about 50/50 split of the newest style magazine and the newest older style of magazine....the most noticable change is the baseplate.

However, they also changed the magazine spring with a spring that is noticeably longer/stiffer.  Has anyone here had a magazine spring failure with the older style magazines with the shorter springs?  I have the chance to get the newer springs for basically no cost, but I'm wondering if its worth it to unload and tear apart about 25 or so magazines to "upgrade" something....especially if there is no point.

Thanks!

Never had any problems with my mags except for the new style base plate cracking in the tab area. When I sent my gun back for a broken slide stop, I sent all my springs and followers to be updated, which they did.

I've only got maybe 600 rounds through mine with a mix of old and new, but I've had no issues.

I've had my M&P9 since 2008. I have 4 magazines & all have been flawless. Hundreds of rounds through each mag & thousands throug the gun. Not a problem with either.