I've been having an issue with my bolt not staying all the way open on the last shot. I noticed it would only be half way open after I fired the last shot. I also noticed when that occurs, I cannot release the bolt by using the slide lock, I'd have to use the charging handle.

I noticed if I hold the charging handle back and manually pull the slide lock back in attempts to lock the bolt open, it appears I can pull the slide lock too far which causes the small piece in the upper receiver that blocks the bolt from moving forward to fall into the recess of the bolt. This allows the bolt to move forward a little bit and makes it impossible for me to drop the bolt by using the slide lock.

Any remedies for this issue? Anybody have this same problem?

Thanks for your time,

Derek

I have not heard of this problem. I would call S&W, they will if necessary fix it for free. Don

__________________
"Don't worry be happy"

Never seen a slide lock, or come to think about it, a slide on my M&P15-22 but the bolt catch area can gum up with firing residue and fail to engage. I think this is a standard M16 part, but it's been a while since I had it apart. Try cleaning and lubricating it. CLP works well.

-- Chuck

I feel like the exact opposite is occuring.

If the area was gunked up I feel the bolt catch wouldn't engage at all. In my instance my bolt catch is engaging too far out causing the piece that catches the bolt to move past the flat area of the bolt into the recessed area. Therefor making it impossible for me to release the bolt without using the charging handle to pull the bolt back first.

So the bolt doesn't release when you smack the bolt stop? I'm still thinking gunk, but am a long distance from your rifle.

-- Chuck

Correct, I'm forced to use the charging handle/

Its hard to explain, especially via the internet.

Next time you have your rifle try to look in the chamber as you pull the charging handle back. pull out the bolt stop as if you were trying to lock the bolt open. you'll see the small piece in the chamber that moves in front of the bolt. Imagine that piece moving too far in that direction, theres a small recess in the bolt that that piece falls into... allowing the bolt to slide forward about a half inch.

I'll see if i can get some pictures to work.

Thanks for bearing with me.

Just tried it. The bolt latch won't move until the bolt is all the way to the rear, then the latch drops and holds the bolt in that position. The bolt doesn't move more than 1/8" (guess) and the bolt stop is across the lower face of the bolt.

I'm wondering if there's a chip out of your bolt stop (possible) or out of our bolt (seems unlikely).

It's NOT an M16 part, but proprietary to the M&P15-22. Shown on the left with a standard lower on the right. The M&P part is ~3/8" above the lower receiver edge.









-- Chuck

I've narrowed down the issue.

This only occurs when the magazine is in. Something about the load assist nob putting pressure on the piece that stops the bolt.

The magazine may be defective. Examine the back of the follower projecting out the back edge. This is what raises the bolt stop to lock the bolt to the rear. Since it's unlikely you have two defective magazines just compare one to another. Best available photo (left magazine):



The other thing to check is the magazine catch. If the spring tension on this is too light the mag catch won't hold the magazine high enough in the receiver and the magazine follower will not raise the bolt stop high enough. (This happens with the M16-series too.)

Normal magazine catch tension is achieved when the catch-bolt is flush with the top of the button on the right side of the rifle. If in doubt push the magazine catch out the left side with a rod and tighten the catch a turn or two.

-- Chuck

Has anyone else experienced this? This started happening to me also and with 3 different magazines.

Remove your receiver halves and insert an empty magazine. The follower flag piece should activate the bolt catch.

Can you press the bolt catch while the magazine is in there with no upper receiver present, moving the follower down?

Yes, the follower goes down when I press the bolt catch release. I just tried it on all 3 mags.

I just tried shooting a few again and it seems that the problem is that the bolt gets jammed and does not go all the way back and lock. It goes about 90% back and if I pull on the charging handle it will lock. grrr.....

I ended up shaving a little bit off the tip of the magazine follower. It prevents it from pushing the bolt catch too far up.

Haven't been able to shoot the rifle yet since this modification, but i loaded a magazine and cycled the bolt using the T handle and didn't have an issue getting a new round into the chamber.

So you did NOT check the tension of the magazine catch?

-- Chuck

Just called S&W and they are sending me a label so I can ship it out to them

I'm getting close to 2000 rounds on my DUR. This phenomenon has starting happening to my rifle now!
Like the op stated, it is hard to put into words but the bolt catch actually gets jammed into a groove in the bolt. It is not a cleaning issue...my rifle was spotless last two trips and had this problem a number of times.

mine actually stays all the way forward and never goes back.. haven't figured mine out yet either. new DUR also.