A Glock .40 S&W/9mm loader sorta kinda works. I haven't had a chance to try it with actual ammo, but it looks promising. I tried it on an empty M&P .40 S&W mag at Sportsman's Warehouse. I noticed that the M&P mag follower tilted backward, probably because the Glock follower is shaped differently. That tilt may not be a problem once you get a few rounds in.
I don't understand why S&W doesn't make a mag loader for the M&P. It's a glaring omission in an otherwise excellent package. Every other double-stack semiauto I've bought came with a mag loader, whether it was a Glock, three different CZs, or my Springfield XD. I don't know whether H&K pistols come with a mag loader, but there are at least aftermarket mag loaders designed specifically to work with those magazines. Sure wish someone would make one for the M&P.
I don't understand why S&W doesn't make a mag loader for the M&P. It's a glaring omission in an otherwise excellent package. Every other double-stack semiauto I've bought came with a mag loader, whether it was a Glock, three different CZs, or my Springfield XD. I don't know whether H&K pistols come with a mag loader, but there are at least aftermarket mag loaders designed specifically to work with those magazines. Sure wish someone would make one for the M&P.