I have a failure to feed problem. With factory match ammo the casing is ejected but a new cartridge fails to feed. With my own reloaded ammo, which I suspect has a lighter load, I have a failure to eject.

This problem started occurring after about 200 rounds thru the gun. I added a Alumalite Thorax Predator muzzle break and the problem got worse. I have since changed out the factory stock to a Magpul PRS and have tried the AR-10 Silent Captured Spring (by JP Enterprises) and the AR10R-XH buffer & spring (by heavybuffers) with no change in the results.

I am using DPMS 10 round magazines.

The only other modification I have made is to add the UTG quad rail system.

I have shot about 600 rounds now.

Here is a short video showing the failure to eject: S&W AR10 failure to eject problem - YouTube

Any suggestions?

jay

Your rifle is short stroking. I would guess that you tweaked something in the gas system, probably the position of the gas block, when you installed the rail. I've seen the exact thing happen before. The gas block has a port in it that has to be aligned with the gas port in the barrel for the rifle to function.

I've had the same issues with my M&P10. Using 150gr American Eagle mostly. I have also made many of the changes as you have with the Magpul PRS, UTG Quad rail, new buffer tube/springs, etc, etc...
ASH, the UTG rail is a drop in and is made for the M&P10 with no adjustment of the gas block/tube. So unless Jay and I both inadvertently bumped, moved, damaged the block while inserting the rail, I'm not certain that would be the issue. I will certainly check though and thanks for that bit of advice.
My M&P is pretty much brand new and I never shot it before I made all of the changes and maybe I should have!!! I now have about 80 rounds through it hoping that the issue would just fade away. Not only was i having failure to feed, I was also having some jam on the feed ramp but the ftf's were more common. I assumed that it might have been due to "cheap" American Eagle ammo.
What did help me was that after the first trip to the range with ftf's at about every 6-7 shots, I brought the rifle home, completely disassembled and used Frog Lube. I heated all the parts with a heat gun before I put on the lube and then let it sit for about 45 minutes before wiping away.
The next trip to the range proved wonders and I did not have a single ftf (although I only shot 10-15 times.
Next trip (with no additional cleaning) I shot about 60 rounds with only a few ftf's towards the end of the session.
It has since been disassembled with a second round of Frog Lube.
The verdict is still out though as i'll have to wait until I shoot again to see the progress.

ImageUploadedByTapatalk1386807398.347522.jpg
Here is a pic of my M&P 10

Thanks for the suggestion. I did have a new muzzle brake installed. The gunsmith had to remove the barrel to thread it so it is possible that the gas block was not properly aligned when he reassembled it. I have tried to realign the gas block and will get out to the range tomorrow.

My suggestion, get rid of the DMPS magazine and try PMAGs. I ordered a couple of the DMPS 10 round magazine and had the first round on both always stuck (dry fire to test the magazine)

Attached Images

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I had the same problem with mine. I tried everything lubing it up, checking the gas block alignment, firing 60 full power reloads (all the while having to treat it like a bolt action), nothing worked. Finally I took it to a locale gunsmith that specializes in military rifles. Upon inspecting he found that the gas port was substantially smaller then every other AR 10 build he had done. He slightly increased the size of that hole assuring me that it was still smaller then a DPMS or Armalite gas port.

Gun has feed everything I have given it since then without a single hiccup. However if this is your issue DO NOT have a joe blow hunting rifle gunsmith do this job for you as it can seriously damage the barrel and make it very unsafe.

Interesting Bassaro!
I will have to look into that if mine keeps having issues. One would think that S&W thought that through?

ok, back to the range this morning... gas block realigned... lubed up.. first 10 round mag of match ammo goes thru without a hitch! I am thinking: 'oh yeah, got this b..... nailed!' second thru fourth mag I am back to a bolt action... every case ejected but total failure to reload the next round... back to banging my head against the workbench...

This is very good advice! Most gunsmith's know nothing about AR's and as a certified armorer myself, I've fixed quite a few including some "custom" builds by "reputable" gunsmiths.

Jay,
please clarify if the issue you're having is feed only or is it also a failure to extract/eject as your video seemed to show? Feed issues could be isolated to magazines, but the other stuff is most certainly gas related. If the gas block is good, then move to the tube. Is it aligned/installed properly? The roll pin is in-place holding it in the gas block, right? Oriented properly? If all that is good, move back to the bolt carrier. Are the gas key screws still tight/staked? If so, move to the gas rings, make sure you encounter resistance when pushing the bolt into the carrier...this is the spring action of the gas rings closing and sealing. If all of that works (can't imagine it will based on the malfunctions you're showing) then I'd send it back to Smith.

If you lurk around enough on other forums you see that quit a few of these rifles are going back to smith for the same issue. I'm willing to wager smith is drilling the gas hole bigger to fix them...

I will admit that after mine was fixed I instantly fell in love with the rifle. It is frustrating however to have this brand new rifle that you've wanted and read about for so long and you find yourself working it like a bolt action. And to add insult to injury having all the guys at the range with their savage axis telling you you spent to much and their rifle does everything yours will for a 6th of the price.

Hang in there man it's a solid fun once you get the bugs out.

Guys. I had lots of problems with in the first few outings. Got home and took buffer out and apart. It had 3 weights and 3 foam pads. I removed the pads and packed in powdered lead. Thing ate everything after that but then it was ripping the casings really bad around the primer. So I took out two layers of lead powder and put two pads back in. I haven't gone out since then but when work slows down I can give you guys a report. Give it a try. If it works, great. If not? I'd send it in.

Good luck.

PS: Bassaro and Ash have awesome advice. I'd listen to them over me. Just sayin.

after realigning the gas block I am now just getting failure to feed - cases are being ejected fine but the next round is sitting in the mag waiting for me to pull the charging handle...

although the final shot does not leave the bolt locked open...

i did follow your suggestion checking the gas system... everything looks find although i don't have any way to test pressure...

will probably send it back into to S&W next week...

Jay have you tried a Pmag in there? Sounds like your gas issue is solved and your mag follower isn't doing its job.

i just ordered them... the strange thing is, until i had the muzzle break installed the DPMS mags were working fine... and given the bolt won't lock back with a single round in the mag... there may still be other problems..

btw, thanks to everyone for their comments and suggestions - i have learned a lot!

Having the EXACT same problem but already using PMAGS. Did you send yours back?

When I changed my MP10 from the carbine stock to a rifle stock, I encountered the same issues using the DPMS rifle buffer/spring. I observed that the DPMS spring was heavier and stronger than the original MP10 buffer spring. When the rifle wouldn't cycle correctly with the new DPMS 308 rifle spring, I put the original MP10 buffer spring back in with the DPMS 308 rifle buffer, and the rifle cycled correctly. I also use a SLR DA7 adjustable gas block, which had to be set almost completely open to cycle the rifle in this condition. Upon further diligence, I discovered that the gas port on the barrel of my MP10 was close to the minimum port diameter tolerance for an 18" barrel. I increased the port size and was able to tune the rifle to use the heavier DPMS 308 rifle spring. Although the rifle can now cycle the heavier spring, I have settled on and tuned it with the following components/moss as it seems to cycle best for me with these components:

a) SLR DA7c adjustable gas block
b) barrel gas port ported to almost .080"
c) Enidine 308 rifle buffer
d) original MP10 buffer spring
e) DPMS A2 rifle buffer extension tube

have not given up yet...

I did try pmags and did not get any different results...

had the bolt sonic cleaned and the gas rings replaced... no different results...

so I put the original stock / buffer / buffer spring back on... and running the bolt really really wet seems to have 'fixed' the problem... ran 30 shots thru at the range and had 1 feed problem and 1 time the last shot did not lock the bolt back... it is a little cold here in new England but I think I will brave the temps and head out to the range again today to put some more rounds thru..

at this point, if things continue to go well, I am going to order the spacer and the reinstall the magpul stock and see how things go from there...

jay

Jayferguson,
Were you running your M&P10 with a rifle length buffer tube without the "spacer"? If so, check out the dimensions of your S&W buffer tube extension, the S&W factory buffer, and the S&W buffer spring. If I'm not mistaken, they are basically using an "Armalite type" 308 buffer system and not a DPMS type 308 system. Using the "Armalite type" 308 buffer system allows the use of a regular AR-15 carbine buffer. And as a result, you have a lot more flexibility in buffer weights to try than when using the DPMS Type 308 buffer system.

well... I got the spacer from S&W... reinstalled the magpul stock and was back to the same old problems...

so I sent the beast back to S&W... got it back after about 5 weeks and they had 'fixed' it by cutting the spacer in half...

went out to the range today and got mixed results... my own reloads did not work at all... factory match ammo was a lot better but still had a few feeding jams and no lock back after the last round...

so S&W apparently thinks it is a buffer issue... so I will play around with that (thanks LlindeX for the armalite info)...

onward...

jay

ok... I tried different combination of buffers, spacers and buffer springs... and on the 3 try... voila! the beast now works perfectly with my reloads and factory ammo!!! I used a heavy buffer spring with the original s&w buffer...

jay

It really depends on who was making those barrels for them.

There has been a few things you would have thought they could have paid more attention to with this particular issue.

Bassaro's fix is one of the possible fixes. If you had no issues with the mags in the beginning, then its' hard to discount them after only a couple of loading cycles. As to ammo, a couple possible issues have been bantied about: The easy one, is the ammo underpowered. If the rifle is functioning correctly, that should not be an issue, with almost any commercial ammo you put thru it.
I am more thinking along the lines of the feed ramps and the overall length of some ammo might be just a bot too long. I would agree to try a Pmag and see how it stacks up with the ammo and how they feed.

Since the rifle already has some changes made to it, I am not sure what the primary starting point is for a fix until a few more questions are answered. How far does the rifle kick the brass out? At what position; as imagine looking down on you and the rifle, the barrel points toward 12 o'clock. 3 o'clock would be directly to the right. 5 o'clock would be over your right shoulder. This will help a bit.
Any scarring on the brass? Is it repeatable, and can you find where the scrapes are being made; this tells which part of function is causing an issue.

I have had a severe failure to feed problem with my new M&P 10. The only mods to mine is the addition of a scope. In looking at the rounds that fail to feed, I see that they are bent at the joint of the casing neck and the bullet. This leads me to believe that the tip of the bullet is getting stuck somewhere when the bolt tries to load it. Upon further inspection, I looked at the chamber and I see that the barrel insert into the upper appears to be a bit too far in. This creates a ridge that is more noticeable on this gun than on any of my other ARs. The picture below illustrates what I mean. I will go to the range again today to try some winchester gray box rounds to see if that improves a bit but judging by the way that the un-fed rounds look after getting stuck, I am afraid I may have to give S&W a call to try to figure it out. To the OP, I am also in MA, not sure how far from me but I would like to get some insight from your experience. Also, if someone else can look at their M&P10 and can tell me if theirs look similar, that will help.
The same ammo on my M1 has no issue whatsoever :-)
Thanks in advance

Jim

HOLY COW!!! What an EXCELLENT set of pictures!!
This is a relatively simple polish job. Take a dremel tool with a small round polishing stone, and carefully massage all that. True up the edges of the barrel to the upper, and then afterwards, use a polishing wheel with some automotive rubbing compound (Rough compound) you will leave that junction slick and this is a problem which can be fixed in about 10 minutes total time. Be patient, and do not push too hard.

Thank you rojo diablo. I figured it could be simple, there's however that feeling about a brand new not necessarily cheap gun needing such work. I would not mind it much had it been a hi-point gun but a S&W? Anyways, I may end up following your advice. Living in the people's republic of MA, I don't want to take the chance of anything going wrong with the shipment or return. :-)
I will later post a pic of a damaged round.

Sent from my SM-P600 using Tapatalk

just to add some detail, here is a pic of a jammed round going in and the resulting damage to the round.

That looks much more like my bolt override condition. It never picked up the new round, just drug it in.

If action is running too fast or too slow, seems they will do this. How far and what position is it ejecting first round?

The rifle ejects fine for the most part with cases lying about 10ft away from me. These pics were taken yesterday. I noticed that my FTF happened only with Winchester white box 7.62x51. I tried, PPU and Aguila besides the winchester. In my case, it appears that the bolt just starts to push the cartridge and looses grip. Possibly because the round is stuck on the ridge I showed earlier or maybe because the area of grip between the bolt and the round is too small. This latter one may indicate a problem with the magazine. The factory mag is a PITA, I have the habit of butting it against the bench a couple of times after loading it so that the rounds seat properly and has worked better since I started doing that.
Anyways, the damage to the round is clear on a relatively new gun.

This is is a bolt over, resulting from short stroking. Winchester White Box is loaded to 7.62 NATO specs which makes less pressure than commercial 308 ammo. If your rifle is running fine on commercial ammo, it's clear that your problem is NOT the feed ramps and the photos show that your ramps are ok.

S&W tuned the M&P-10 to run on commercial ammo because that's the spec hunting ammo is loaded to. If it were tuned to be used with 7.62 NATO ammo, it's possible it'd be over gassed for hunting ammo with sharper recoil than necessary. You can tune your M&P-10 to run on lower pressure ammo, but the result will be the same as tuning a 5.56/223 caliber AR to run reliably on low pressure ammo- when using full pressure ammo, recoil will be sharper and the reciprocating mass will bottom out harder

Not sure if it means anything, but my old DPMS LR308 that shot everything without any need for mods had a barrel stamped 7.62 with a larger gas port. The M&P 10 barrel is stamped .308. Is there a relationship between the .308 designation and the smaller gas port?

The .308 is the hotter round of the two, so my guess is that less gas is needed to cycle the BCG.

Looking at Armalite and DPMS, their AR "308" model ads specifically address 7.62 NATO and .308, but the Smith & Wesson ads do not mention 7.62 NATO at all for some reason.

What's the difference between win white box and the commercial ammo you speak of? I mean besides the .308 and 7.62 issue? I don't shoot reloads unless white box is a reload :-)
Also, I think the manual states that both types can be shot.
Thanks for the comments.

White box tend to be military/government ammunition.

I've shot white box and been fine. Apparently, not everyone is so lucky. Just like any other firearm though, it seems each individual M&P10 likes some ammo better than others and hates others.

As an example, my Catamount Fury won't cycle with low brass and some low recoil high brass no matter how I adjust the gas block even though Century Arms and the Owner's Manual says I should be able to.

What ammo the manual says the rifle will shoot & function with and what the rifle actually shoots & functions with, are sometimes different things

I'm new here but have used info so much I decided to join. I have a Smith M&P 10 also with many of the same problems listed here in this thread. I've added one Tubb's Precision AR-10 CS Buffer spring, a CMC 3.5 pound trigger group, and a 3-12 UTG scope. The trigger is very nice but I won't go into the install since that's covered here in another thread. When I use any .308 round I have zero issues and fairly good accuracy at 100 yards. That's any .308 I've used from Federal to PMC and a few in between. I've never had good luck with any 7.62x51 ammo. Failure to feed and failure to lock back after last shot. The only change to the system to affect it is the spring which made it operate smoother. This gun is for .308 and if you find it, hotter 7.62 rounds. I like the gun. I like to run .308 and now I'm looking at the right weight .308. From the threads here it looks like it's closer to 168grains then to 150. Please, since I'm new, let me know if I've missed anyone having problems with the .308 round not cycling the rifle correctly.

Actually, commercial 308 ammo is loaded to higher pressure than 7.62x51 ammo

Mistwolf. I guess I made an assumption that everyone here would know that .308 is a higher pressure,thus, it would cycle the bolt better with less fail to feed due to short stroking problems. At least that is my experience with my M&P 10 and seems to be a common problem. I'm thinking an adjustable gas valve would be the ticket like on the Ruger 762 and a few more. The gas port would be another place to look but I like to start with less drilling at the beginning of troubleshooting.
Thanks by the way. My shooting partner that has years of experience over me didn't know .308 has higher pressures.

An adjustable gas block will not help an undergassed gun. The issue is the gas port size.

You can allways gas down with an adjustable block, but you cannot gas UP, because it is running wide open now! It only receives what comes out of the port!

Please read my comments in the other related thread just below this one.

In the case of S&W 10, COMMERCIAL means US made hunting ammo and match ammo by US makers.

Also thanks for the link to your thread. It helped a bunch!

I'm a little chagrined. I went back and read your post again and realized I misunderstood it the first time.

The more I shoot the Big Smith, the less picky it is about ammo. I've recently swapped the carbine buffer out for an H buffer and the rifle functions fine on handloads that duplicate military ammo without opening up the gas port. However, I'm also using a BABC which I suspect increases back pressure a bit

I've been hoping to get to that point of less picky and one of the next steps for non-destructive improvement would be the buffer. I'll have to weigh mine since I haven't yet. I like the "Big Smith" comment. I'm going to use it myself now. I'll be at the range tomorrow and using Gold Medal Match .308 168grain. If the gun likes it, then I'll mimic the load of the GMM with a 168grain bullet. I do want this gun to be the gun to carry into trouble or to ideally keep trouble away until help arrives. However, 00 buck in a dark hallway would be the first choice......Thanks again! Tell me what brand H buffer are you using?

I don't know what brand the buffer is. It's a spare I picked up along the way. It's the type with 1tungsten and 2 steel weights

Sounds like an H buffer which is 3.8oz if my research is good. I'm still researching the change to another buffer which may cause short stroking if I don't chose the correct weight. I already have short stroking with the 7.62 ammo so I may have to accept the fact that this gun is made for .308 which I think you mentioned in one of your posts. My range day was perfect with .308 ammo. I was way more accurate with the Gold Medal Match 168 grain. So, I'll sit down to a long research session to see which rifle will fire both nato and .308. I think this rifle will be more appealing to a future buyer if I don't drill or cut into it and leave that to the next shooter.

Yea, well, told you so! What kinda groups did you get with the GMM?

You do not have to research anything, it was made to CYCLE US made .308, but it works just fine with 7.62 if you give it a little more gas to work with.

If you want to make it more appealing to a future buyer, you might try selling them a gun that just works with what you put into it!

Oh, and BTW, even at my .073 gas port setting, I am still pushing a H2 buffer to soften things with no issues thus far.

To me, I just want it to work! I may decide to punch a bunch rapid fire one day, then go to precision the next. The gun needs to work! And with what I feed it!

And yes, at the cost of GMM, I can load it myself at half the cost, or buy decent reloads in Amax 168, which have done better thusfar in my gun.

You might try Freedom Munitions.com as an example for some good quality reman Amax at less than a buck per. First order is free shipping!

Do as you like, just sayin.

The GMM surprised me at 3 MOA with 3 of the 5 holes touching in a straight line. 2 flyers but that was me. A little more work and I should have that spread a little tighter but for what I'll use it for it's great grouping. I'm leaning toward the enlargement of the gas port because like you, if things go like we're seeing in the news then I'll need to fire what I find which most likely will be 7.62. I do have plenty of that. I'll reload to the GMM specs when I do another round of .308. I'll check out your Amax link, thanks!

I guess it depends on the rifle. Lake City 7.62 has been running fine in mine so far.

Yep, at least it has US powder which probably helps! Burn rate is an issue!

How is your ejection pattern?

These things are NOT AR-15, yet same principals apply to an extent. Not sure to what extent.

On a typical AR, a pattern from 1 o'clock to about 5 o'clock is a scale. (over and under gassed) with 3-4 o'clock being more ideal range.

Ejection has been about the same as shooting match rounds. About the 3-4 o'clock range, with the occasional 1-2 from both. It doesn't happen often but when it does, I have to go outside the shooting shed/house to get them. Otherwise, they are all inside the shed and I have to pray the brass hasn't fallen through the gaps in the floor.

I really need to get a brass catcher. It's not like they are all that expensive or anything....

OMG!!!!!!!!!!!!! DO NOT use a small round stone! This is what cratex polishing tips are made for. Much harder to do excessive damage with, but still capable of doing the job.

While true, since the item is still under warranty, you'd be better off to send it back, with a set of those pictures to illustrate what you believe is the cause of the problem. I'd include a couple of pics of those bent rounds.