Failure to feed problem

[jayferguson]

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

 

[ASH556]

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.

 

[avpropres]

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.

 

[avpropres]

Here is a pic of my M&P 10

 

[jayferguson]

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.

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.

 

[Sonny Gunny]

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)

 

[Bassaro]

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.

 

[avpropres]

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

 

[jayferguson]

yet again...

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...

 

[ASH556]

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.

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.

 

[Bassaro]

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.

 

[Deeked]

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.

 

[jayferguson]

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.

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...

 

[Jack07]

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.

 

[jayferguson]

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!

 

[CVE]

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

 

[apiccola]

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

 

[jayferguson]

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

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

 

[LlindeX]

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.

 

[jayferguson]

update...

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