This is a first for me. I've got dozens of semi-autos and never had this problem......

Just picked up my new M&P 9c yesterday. This morning I did the field strip to remove the packing grease (oddly, there was none). Anyway, I'm familiar to the basic procedure of taking down the pistol as I own a Shield which is similar, i.e., the "sear deactivation lever" must be down into the mag well, etc. I lubed the gun, then reassembled. I did note that at some time when I was lubing, the sear deactivation lever somehow flipped to its up position. I did not pull the trigger or manipulate any of the other controls, so I suppose it just flipped down as I was rotating it around to lube it. I put the deactivation lever down again, and reassembled the gun. No issues there.

I inserted the magazine (which pushed the deactivation lever up), and attempted to have the slide go forward using my left hand to draw it back, then release it. Nothing. So then I tried depressing the slide stop lever...first one side, then the other side. Nothing...the slide stop button will not go down. I then tried using my left hand to push the slide back while depressing the slide stop lever. Nothing. No movement in the slide release button at all.
Then I removed the magazine (slide stayed back as it should). I then repeated the two methods of releasing the slide without any problems. I did note just using the slide stop without assisting with my left hand was a little difficult, but not much for a new handgun.

Any ideas? I know I can call S&W but I figured I'd ask here first, hoping it's something simple than I screwed up and can easily fix!

Oh, I did field strip a couple of times before I wrote this, hoping I could correct whatever problem is there to correct......

I don't ever even mess with the deactivation lever...Empty mag in to lock the slide back and out to cycle it closed. To disassemble, empty mag in, lock the slide back, throw the breakdown lever, take the mag out and cycle to close, then pull the trigger and take the slide the rest of the way off.

The mag follower is supposed to push the slide lock up when empty. Simply pulling the slide rearward will not release the slide stop.

The mag springs are crazy stiff when new. Trying to manually press down the slide stop on an inserted empty mag requires much force. You may simply not be pressing hard enough.

So in the end, this sounds normal to me.

I do not release my slide with an empty mag inserted. I drop the mag , even if it's only and inch, then release the slide.

A few other semis I have provide enough leverage to press the slide lock down with an empty mag. My M&Ps typically do not. It's even tougher on a Shield.

Well son ofa gun; you're right.....nearly!

With my Shield, I can easily close the slide with an empty magazine inserted. Same with my other, non-S&W self loading pistols.

But I did insert one round (that was quite stiff!) and yes, I could then use the slide release to close the slide. I did have to help it a bit with my left hand moving the slide backward just a bit. I suppose that's all just the nuisances of a new pistol. But man, I have NEVER had such difficulty loading just the first round in any double stack magazine! On my Shield it's difficult to load the last round, but the first goes in without effort. The first round with the 9c's magazine I loaded to do my test I did without putting the base of the mag on a solid surface, like my desk. However, I did load 12 rounds in the 9c's remaining magazines by placing the base of the magazine firmly on my desk, and they loaded okay. I'm going to let my three magazines "rest", fully loaded, until I get a chance to shot this new pistol in a few weeks! Hopefully the next magazine loads will be much easier.

Thanks for the reply - you hit the nail on the head. Just goes to show that even when we think we know a lot about something, there is always more to learn!

Yeah, I know about that trick. I have done that with my Shield occasionally. But with this new pistol, I wanted to follow the manual exactly....sometimes I am a little anal-retentive!

Thanks for the suggestion.