So today my M&P10 Sport essentially became a single shot for the time being. I’ve had it for about 8 months and have shot it multiple times with no issues until today. When I fire a shot the spent casing is not being ejected. It is staying in place and needs manually ejected by cycling the charging handle. It is not double feeding or stove piping. The spent round doesn’t seem to be cycled at all and just stays put. When I manually rack the charging handle it ejects the spent casing and loads a live round with no issues.

It shot fine prior to a recent mod I added so I’m not sure if I messed something up. I added a Radian Raptor charging handle after following the M&P10 needed mods for removing material from the step in the channel of the Raptor charging handle. It worked fine at home manually charging it and cycling rounds through it. However this problem started the first time firing it with the Raptor charging handle installed. I tried multiple ammo brands and tried both .308 and 7.62x51 to eliminated ammo issues. I also reinstalled the factory S&W charging handle that I added a Strike Industries latch extension to and the first round fired and cycled normally, but then each round after that continued to not eject and needed to be manually ejected by racking the charging handle.

This is my first semiautomatic rifle so I am not sure where to start to resolve the issue. Any suggestions on where to start is appreciated.

Troubleshoot the problem. I doubt the charging handle is the issue if it moves easily enough when you move it but just to be sure, lock the bolt back so you aren't working against spring tension from the buffer spring. Work the charging handle back and forth and make sure it moves freely. Remove the charging handle and compare it to the one that came with the rifle doing the same thing.

If all that seems to be fine and about the same, I would look at your gas block and gas tube. Is the gas block solidly locked in place? Is it at the 12 O'Clock position in relation to the top of the rifle? The gas block squarely up against the ring on the barrel? Meaning, it hasn't shifted forward away from that has it? If gas can't go through the gas block and through the gas tube back to the bolt, the bolt can't cycle.

Look at the end of the gas tube where it enters into the area that the bolt carrier cycles back and forth. Is it round and straight and not crushed or bent? If the tube is crushed or not going into the gas key, the gas can't get into the bolt carrier to cycle the piston portion of the bolt so the action can operate.





These pictures should help some.

Thanks for the detailed info and photos. That gives me a starting point. I will check it out. I was thinking it was possibly gas related but this platform is still really new to me. Thanks again.

Also take a look at the gas key on your BCG. Make sure it's still tight and properly aligned. They are supposed to be securely staked in place, but sometimes (rarely but not never) they still work loose. They can also be damaged if dropped just right on a hard surface.

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Or something like that . . .

This is what the staking should look like.

Welcome back JD, if you will check back to your post inquiring about this seeming very simple mod in Feb, you will note I liked Eric 300's post about listening to Smith and Wesson and Radian Raptor... LOL

Like you, I was a prolific "modifier" in my early years, after deciding engineers didn't know ****!! and I modified dang near everything I owned, (put headers on a 72 Nova, died the first time it rained and I drove to church), and left a trail of "improved products" that were iffy on functionality, but they were all "better" after being modified by me...

Sorry for the "observation" now lets get back to your rifle's sudden intransigence.. (did you know all rifles, vessels, and aircraft are female? I didn't think so??), sometimes to much affection may result in "sudden onset independence"?? sorry to our members of the "fairer sex", (no that's not a reference to judicial equity, nothings ever fair when dealing with the superior intellect and emotional maturity of a Lady), I do have 7 daughter's, and yes I always lose...

Now back to your little rifle, she was working, and you disturbed her perfect harmony, with your own attempt to make her "better"... (yes, just ask your wife) that's a "no no!".. as Sgt Sandman has so accurately observed? its most likely a problem with your gas system, check that your gas block has a credit card width gap between the rear mating surface and barrel flange at the gas port... see Sgt Sandman's picture, that gap is to allow the front plate of your delta ring handguard between the barrel flange and the rear surface of the gas block..

pop your upper off, plug the breach end of your barrel inside the barrel extension with your finger and blow into muzzle, you shouldn't here any air leakage at the gas block/gas port, but you should hear a rushing sound like a blowing gale through the gas tube and into your upper receiver, and feel NO back pressure what so ever, NONE! if there is a restriction, your gas block is misaligned!

also check that your gas tube ends at the middle of the "cam pin cutout" inside your upper receiver as in Sgt Sandman's other picture..

report back your observations for further diagnostic's...

Outstanding post Sgt, I'm a little sad that I lack your eloquence...

Well I got a chance to take a look at my M&P 10 Sport, which was not extracting the empty rounds. It was as if the bolt wasn’t moving at all. I took the bolt and extractor apart and didn’t notice any issues though with the extractor I wasn’t completely sure what to look for other than it moved freely when pressed down. The gas key was good and tight as well as staked down. I did notice that the gas block had at some point slid forward about 1/4” inch, and the bolts were not very tight. It looks like the factory sling mount is hitting the bottom of the picatinny rail of the quad rail hand guard I put on it. So I’m not sure if that could have somehow worked the gas block forward. So I slid the gas block back in place and tightened it down and took the hand guard off to see if the gas tube was aligned and everything looked ok. So I put the factory charging handle back in with the factory latch and went to shoot.

I fired 3 rounds. The bolt now moved and partially ejected the empty casing on all 3 rounds. However the empty brass casing was jammed twice at almost a perpendicular direction to the ejection port and the third shot was parallel to the ejection port but stayed jammed ahead of the bolt. All three empty brass casings had to be ejected manually by pulling the charging handle. The empty casing also had a flat spot on on side of the neck as well as two vertical scratches in the one side of the neck leading up the side of the brass casing. I attached a few photos of the emptied brass. Any more suggestions or what direction to head next with trying to solve this issues is again appreciated.

Well, the gas block is the problem. It sounds like it's still not completely where is should be and now it's short stroking but at least it's now sending gas back to the bolt carrier.

The gas block not only needs to be snug up to the shoulder of the barrel but the port in the barrel needs to be aligned to the port in the gas block. That can be a bit tough. Slide the gas block forward and look for the markings where the set screws tightened to the barrel. There should be two sets. Possibly right on top of each other.

Now look at the port on the top of the barrel. Does it look to be clear? If so, the best thing to do is to take a carpenter square or something similar and butt the "L" part of the square against the shoulder while lining the square up with the port in the barrel. Draw a line with something that will be removable after you installed the block like a marker or something that will wipe off with a cleaner. Make sure the mark is long enough to be seen after the gas block is in place.

Next is going to be a bit more difficult. You need to mark the gas block with a line that shows where the port in the gas block sits. You need to do this in order to be able to get the two ports to be properly lined up.

You could remove one of the set screws in the block and try to line up the screw opening with the marks made on the barrel from the set screws but if they are pretty much on top of each other, how are you going to know which mark or where on the marks you need to line up the hole with? The method I mentioned will be more reliable.

Lastly, put some thread locker on the set screws so they don't work loose again. Don't use red. Not unless you plan on using a torch or drilling out the set screws in the future when you decide to do some work or replace the gas block with something else. Blue is generally the best choice. It holds pretty well but will allow you to remove parts later on without too much trouble.

Well I gave it another go today trying my best to measure and mark everything out to get the gas port holes in the barrel and gas block aligned. I also tried it using a makeshift gas block alignment pin similar to what I saw on a gas block alignment video from Brownells. The pin fit through both gas port holes in the gas block and the barrel aligning both port holes. So, I drew the set screws down and also added thread locker. I took it to shoot and got the same exact marks on the empty cases. It also still short stroked jamming the empty casing in front of the bolt and parallel to the ejection port. I guess I might have to get someone to check it out at this point.

JD, if you check Sgt Sandman's first picture, you will see that the gas block is supposed to have a gap between the barrel flange and the back of the gas block.. that is to accommodate the forward rim of the delta ring handguard.. Don't ask me why, but they set them all up the same.. look at the gap on Sgt Sandman's picture, approx a credit card width to line up the gas port on the barrel.. did you block the back of the barrel and attempt to blow through the muzzle, if its blocked, move the gas block until you can feel/hear it flowing freely and tighten it down right there.

I saw your post on AR-10 Builder's Page, I am a mod over there, sorry you are still having problems, you likely need to drill gas port up a size or so if its no cycling with the gas block properly aligned.

So I tried realigning the gas block again. So success on fixing the issue, is back to only moving the bolt part way and then jamming. So today I boxed it up shipped it back to S&W. I guess now they can figure it out hopefully. Thanks to everyone for your suggestions and help in trying to fix the issue.

So do you have your rifle back yet JD, any news... don't be surprised if it just shows up on your door step...

Got it back on the May 19th. They didn’t notify me other than that tracking number when it was shipped. They told me they would call and let me know what the issue was and when it shipped but I guess they just shipped it back and sent the tracking number.

So I got my M&P back a few days ago. I haven’t gotten a chance to fire it yet, so I don’t have much of a update yet, but the return process was smooth so that was a plus. I would have preferred to know what the actual issue was that was causing the problems I was having, but all I got was a paper shipped along back with the gun saying it was inspected and that the upper assembly was repaired. So that description doesn’t really tell me much. I called to see if they could give me a better description of what was repaired but was told that the gunsmiths were not available to speak to on the phone since they were upstairs and the rep on the phone had no other details other than what was listed on the paper. Once I fire it I will give an update as to how it went.

I was able to talk to a different S&W customer service agent and I asked if there was any more details regarding the vague description of repaired the upper assembly that was listed of the last that was shipped back to me along with my M&P10. The lady on the phone said there was a note in the file saying the gas port was drilled out bigger to 1.85mm or 0.07283”. I’m not sure what the factory drilled gas port hole size was but this leads me to believe that the techs at S&W felt that my gun was under gassed which caused my issues. Though I am still a little confused that it worked fine with .308 ammo until the day the failing to feed started. Then it was having issues with both 7.62 and .308. I hope to get a chance to shoot it some this weekend and see how it works.

Well the weather was nice this evening after work so I took my M&P10 out and fired some rounds through it. I fired several rounds of American Eagle, PMC, and Aguila branded ammo in both .308 and 7.62, and the gun fired and functioned fine. No failures to feed or short stroking. It does seem to eject the empty brass out with a bit more force than it did prior to S&W drilling out the gas port. So at this point I am very pleased with outcome and service that was provided by S&W.

I also fired each type and brand of ammo with the factory charging handle as well as the Radian Raptor charging handle that I was originally trying out when my issues all started. Though I did modify the Raptor charging handle a bit by removing some of the hump on top and the channel as others on here had mentioned sometimes needs to be done to use it in the M&P10.

And here we have the answer JD, I'm very happy that Smith and Wesson followed my suggestion and that your S&W M&P10 is now a fully functional weapon,, good work JD, good work Smith and Wesson...

Some here have mentioned about doing that in the past. It has me wonder what is different with your rifle that it needs to be opened up vs. mine that has ate everything I've fed it with no problem.

I have been wonder the same thing. For months mine functioned fine also using different brands of ammo and then one day started having the ejection issues. I was able to talk to one of the gunsmiths at S&W and asked him about drilling out the gas port. He said drilling out the gas port is the easiest fix for this issue since they didnt drill it out much bigger than it was from factory. He carbon build up or brass build up can plug the gas port hole. Another thing he mentioned is that a burr could possible drop into the hole after several rounds. No matter what caused it, my M&P10 has been functioning flawlessly since getting it back. I shot several rounds through it again today using 5 different brands of ammo in various grains in both .308 and 7.62 and not a hiccup today.