New m&p10 cycling issue

[Little Creek]

I got my M&P10 about a month after the SHOT show from the initial delivery of 100 to a LE distributor. I believe this firearm was built in the first batch. I cleaned it, including the BCG, with Hoppes #9 (I am old school) and lubed it "wet" with Hoppes Elite Gun Oil. Since then I have fired exactly 100 rounds of 308 150grain PSP deer hunting ammo from one of the major ammunition manufacturers (made in the USA) with no issues. I am not yet ready to clean or oil it again. It came with a PMAG 20 LR. I bought a 10 round metal magazine, ACS I think, just because I found one for sale locally. I shot it with both magazines. I think it shoots very close to 1 MOA, with hunting ammo, except for the shots I screw up. I have had no feeding or reliability issues.

I recommend (if you are having functional reliability issues), clean it throughly with a gun solvent (not a degreaser), lube it throughly with a gun oil, and shoot quality ammo from a major ammo manufacturer. Mine is one fine 308 carbine.

 

[Swannie]

I've already sent my rifle and magazine back to S&W to let the experts look at it. I'll let y'all know if they tell me what was wrong with it.

I called S&W today just to get a time frame on how long they typically keep the guns for warranty work. It takes them about 3 weeks. So it will be a few more weeks before I get to take it back to the range.

@CC426 My rear take down pin is way tight also. I have to use something to punch it out before I can pull it the rest of the way so I can field strip or clean.

 

[unknwn]

"...rear take down pin is way tight also..."

Drop the grip assembly and find your pin detent spring (not the safety detent one though) and cut a couple of coils off of it. You might want to do it more than once to get things to your 'druthers. A thin abrasive wheel on a dremel works better than side-cut/dyke pliers.
I found my safety detent spring bent from factory assemble.
When I replaced my grip and put in a new spring, I found that detent pretty stiff too. I think that the well the spring goes into is too shallow on some grips. I ended up cutting that one too.
Either of these springs are not terribly particular about length and can be tailored for best feel of their controlled part.

 

[Swannie]

I finally got my rifle back from S&W. All the report said was that they repaired the barrel and replaced the magazine. I called S&W customer service today and they couldn't give me any more information than that either without finding the gunsmith that worked on it and ask them.
@ Unknown I think they loosened up the rear take down pin too. It was much easier to take the rifle apart when I got it home. I could actually pull it out by hand once it got started.

 

[rojodiablo]

I finally got my rifle back from S&W. All the report said was that they repaired the barrel and replaced the magazine. I called S&W customer service today and they couldn't give me any more information than that either without finding the gunsmith that worked on it and ask them.
@ Unknown I think they loosened up the rear take down pin too. It was much easier to take the rifle apart when I got it home. I could actually pull it out by hand once it got started.

Re-seated the chamber cut and polished the bore of the chamber.
It's a common thing on the DPMS platform rifles. They tend to have a slightly rough cut in the chamber......(Most rifles actually do. It just does not affect a bolt rifle, as they load and unload much more slowly and deliberately.)

Before y'all start squealing, I do not mean 60 grit sandpaper rough, I mean not slick polished. A small chatter ring inside will hang ammo 'till the cows come home on a semi with a long piece of brass in it.

 

[H60sar]

Be sure to check the bolt ring to ensure they are not in line. Mine was, fixed it and was OK.

 

[Ltorote]

Cycling issues

I had similar cycling issues. Of course I bought a 1000 rds of CBC, which was complete ****. Tried a 100 rds or so as single shot rifle. Traded for different types of Nato ball, and sold the rest. Bought what ever I could find at Wal-mart, Win Super X, Fed blue box 150 gr, and 1000 rds PRVI 145gr. The Super X was the most consistant, various Nato ball short stroked quite often, jammed less often. PRVI short stroked every one or two, jammed every 4-5 rounds. I tried an H2 buffer which stopped the jamming, and reduced but did not eliminate the short stroking.

I took it to a local armorer, the gas block was lined up ( I left a gap exactly 1/2 of the delta ring plate thickness), however he moved it all the way back (YHM-9383) just to be sure. He also suggested using 168 gr ammo since he thought the 145gr PRVI was leaving the barrel before the bolt cycled.

I had seen that the gas port was supposed to be 0.068". So I tried to insert a 1/16" drill bit (0.0625") but the port was too tight to insert. I decided to drill it out with that bit, careful to make sure the bit was well short enough to not touch the other side of the barrel, and proceeded to drill the port. Since my next bit size was 5/64 (0.078125) I decided to just slightly ream the hole with the 1/16 bit. I re-installed the gas block all the way back.

Well upon returning to the range I am happy to say this gun finally runs like a champ ! I finished up chronoing some hand loads and proceeded to the long distance range to check the loads.

Not one single short stroke or jam with around 50 rds handloads, and around 100 rds 145 PRVI FMJ. I loaded 3-5 rounds in the mag at a time, and the bolt held open every time on the last round. Problem solved.

I had contacted S&W who wanted me to send it back. However, I had upgraded the hand guard, installed LP gas block, installed a RRA 2-stage trigger, AAC 51T muzzle break, and ergo hand grip so I did not want to take all that stuff off to send back to them unless I absolutely had to. Thankfully that was not necessary. She runs like a champ now.

 

[copemech]

You see this thread runs way back in time. Glad you seem to have yours sorted, or maybe?

You may find a number of opinions on this, yet I can tell you my gun would not run reliably at .068 with all ammo.(cheap ****)

Marginally undergassed would be my term for it.

Being a bit conservative tinkerer, I took my port out to .073 and things started to work, not just better, but really work!

Just how close to the edge of ultimate reliability with whatever I feed the gun am I now? Unsure? I have since seen evidence that a .075 port as standard in similar mid length configuration by premium barrel mfg. for others such as DPMS. No cheap **** here in a $500 barrel!

Maybe they know something? Frankly, I should have done it when I had it apart last, I have the number drills, and they can be had cheap so you are not dealing with common fractional set, you can get what you want.

Add the fact you can allways gas down with an adjustable block, but you can't go up if you do not have the port!

I also have seen that .090 is not uncommon in .223 guns, yet I have not studied length configurations on this.

So all can take things into their own consideration here with their own ammo and usage, but my current plan is to go to the .075 route next time down for maintenance to get further from the edge of unreliable function.

Chime in Rojo!

 

[fstkmaro]

Im waiting for the return label from S&W to check mine. I am sure the barrel will need re-seating and chamber check. Hopefully they'll do it within their 3 week advertised period so I can shoot it before fall comes in

 

[chkv]

You see this thread runs way back in time. Glad you seem to have yours sorted, or maybe?

You may find a number of opinions on this, yet I can tell you my gun would not run reliably at .068 with all ammo.(cheap ****)

Marginally undergassed would be my term for it.

Being a bit conservative tinkerer, I took my port out to .073 and things started to work, not just better, but really work!

Thanks for this. The exact same thing worked for me. Before opening up the gas port, mine would FTF on anything from cheap to match ammo. The cases would always eject around 5 o'clock even when I added an adjustable gas block on almost any setting. Now they eject right around 3:30 and I haven't had a single FTF in over 100 rounds using four different types of ammo.

 

[Fafhrd]

This message is from a year ago but I had the same issue with the P Mags and NO issues with the original magazine. I took the original and the P mag and looked at the end top front where the shell comes out from the magazine.

The orignal magazine has NOTHING...no funny little curves or guide. The P Mag had SHARP corners on the shell curved arms on the top. sharp edge catching the gap in the end of the shell. The front had a opening and was high so the ridege on the cartridge Caught on the casing edge. I crimped each bullet and it helped.
Finally I got my Dremel and cut 1/2 inch off the front of the magazine so it looked EXACTLY like the original steel mag and lo an behold NO MORE MISFEEDS. The bullet went smoothly into chamber and came out with no hang ups. Even my reloads work great with the mag modified.

 

[Robert1]

Disassemble the mag gave it a good cleaning took a very fine file to the inside top of the mag worked like a charm. It was scratching the brass.