this post was submitted on 10 Jul 2023
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So my relatively new s&w m&p15 won't cycle the action when shooting. The hammer will reset but the bolt wont move at all. This happens with several different ammos, both winchester 223 and winchester/ federal 556.

First thing i did was clean and oil it. No difference.

Then I checked the bolt seals and they are in good shape. When standing the bolt up on it's extractor side it doesn't move, but will with light pressure.

I figured something must be wrong with the gas tube so I blew some carb cleaner through the gas port in the action (the nipple that interfaces with the gas key on the bolt). I expected it to be blocked but the cc ran out the barrel unobstructed.

I covered the gas port (in picture) with a piece of masking tape when shooting and gas came out enough to discolor the tape but not blow a hole in it. I know that's not super scientific but nothing wrong with more info.

I honestly can't think of anything it might be. Any info helps, thanks

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[–] [email protected] 6 points 2 years ago

I’m sorry, but you covered the gas port on the gas block with tape and it didn’t blow it off?

Your gas block or barrel must be severely misaligned causing the gas block and gas hole on the barrel to not line up, leading to it choking off the gas.

[–] [email protected] 2 points 2 years ago (1 children)

What rounds have you tried? Apparently they have problems with semi autos, and work well with standard and high velocity rounds

[–] [email protected] 3 points 2 years ago (1 children)

Just standard ball winchester ammo for 223.

My 556 is federal green tips

[–] [email protected] 3 points 2 years ago* (last edited 2 years ago)

http://smith-wessonforum.com/smith-wesson-m-p15-rifles/700774-m-p-15-sport-2-not-cycling.html

Here's the S&W forums with someone else who had the same issue a recently. Theirs turned out to be out of spec and needed to be sent into S&W.

Could be a mag that it doesn't like(loose spring/ bent lip). The block and barrel port might be misaligned. The advice there was to make sure the whole bolt carrier group is lubed up and to check to see if the carrier key is loose.

[–] [email protected] 1 points 2 years ago (1 children)

Have you checked that your recoil spring isn't jammed or obstructed?

[–] [email protected] 1 points 2 years ago (2 children)

Yeah it's in good shape. The rifle cycles manually, maybe just a hair more resistance than I'd expect but tbh this is a new platform for me.

[–] [email protected] 1 points 2 years ago

They're pretty simple devices, so it sounds like there's probably an issue with your gas system. Can you take it back to where you bought it?

[–] [email protected] 1 points 2 years ago

They're pretty simple devices, so it sounds like there's probably an issue with your gas system. Can you take it back to where you bought it?

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