I went shooting today and when I was just about done I noticed the right side selector had fell off. I found the lever but not the screw. Is S&W pretty good about sending parts?

Not really. My last order took one day short of 6 months. I wish I was kidding.

I ordered some parts the week of Thanksgiving. They were delivered the week after Christmas.

That's not what I was hoping to hear . Maybe the gun shop I got it from can help. It's just a teeny tiny screw lol.

I have a pic of mine if you need it. I figure it is not that special that you cannot use something else in the mean time. Prolly a 4-40 thread or so, tapered allen. 1/4 oal I would guess.

Mine was tight, but no blue locktite on it. But it will have some soon.

Well, it's not a #6-32. I got one of them from work. The gun shop I got it from said it's probably a #8-40. He may have meant #4-40. I'm going to the fastener shop here to see if they have one. I really don't want to wait 6 months to shoot my rifle again

Update, I went to the fastener store around the corner from me and told him I needed a screw smaller than the 6-32. He had 3 different sizes so I took all 3 since I could not find what size it is on the internet. Luckily one fit. I'm not sure which one though. It took a 1.5mm Allen wrench. I still want S&W to send me one so I'll have a spare.

When you replace it, don't forget the blue lactate…
Loctite 0.2 fl. oz. Threadlocker Blue 242-209728 at The Home Depot

I just talked to someone at S&W. They will not send out parts for the M&P 10. Not even a screw. He told me I would have to send it to them to be repaired.

It's aggravating, but the small ambi safety lever falling off does not render your rifle inoperable. You just lose the ambidextrous safety.