More rookie questions

[TexasE]

I finally got my scope and mount so I took out my new MP10 for break-in and sight-in.

I was able to sight in pretty quick and was hitting 200m steel withing 20 shots. Good stuff.

I was also jamming every other round. Actually damaged a few unfired rounds as fresh round was wedged under the spent round in the upper. Had to use a tool to push the fresh round back into the mag so I could eject the mag.

Here is what I found. I just want to see if I am on the right track.

1) When I pulled the takedown pin the buffer and buffer spring shot across the work bench. I inspected and see no damage. I can reassemble and it works normally except if I manually cycle the buffer (with a finger) it seems to rotate a bit. Have any of you had this happen.
side note: the buffer rattles internally. Is there a secondary mass in the buffer? Is this normal?

2) As per the instructions I cleaned the gun prior to shooting it. I applied oil very lightly as I would in any of my handguns. A drop of oil on my fingers and "message the moving parts. After shooting I found the gun DRY. No sign of any lube (or wear). After cleaning and going a bit heavier on oil application I notice the bolt is much more free that it was before or after firing. Is this normal? Does the gas system burn off all oil in 80 rounds? How "wet" do you run your AR?

3) I found the piston rings had migrated so that two were stacked with the gaps aligned. As per the manual I had made sure they were staggered prior to reassembly when I first cleaned it. Maybe lack of lube?

Have any of you experienced these issues before? Could any or all of these issues lead to feed/extraction issues I had?

Thanks in advance!

 

[sgtsandman]

1. Does the buffer tube partially cover the buffer retention pin? If not, that is why your buffer when flying. The noise in the buffer is normal. Typical buffer spring twang.

2. Your bolt carrier group needs more oil in key parts. I'll try to remember to post up some helpful illustrations for that when I'm on my computer.

3. The piston rings will some times spin. Even with all the slots aligned, the rifle will still run. It just will have a little decreased performance. As far as lube. The previously mentioned illustrations will address that.

The feed and extraction issue is something else. It could be lubrication, a mag issue, or a couple of other things. Lets see if we can narrow it down a bit. First, what ammo are you using? Brand and model. Second, when they do eject, where do they eject to in relation to a clock dial face?

 

[sgtsandman]

How to lube your AR and where

 

[sgtsandman]

AR ejection pattern and what it may mean

Ok, this is not saying what is wrong with your rifle as far as feeding and ejecting but it may help in discovering what may be the problem. Not to mention it may help in the future.

Part of the reason I'm asking about the ammunition, is if you are using steel, the coating on steel ammo is known to stick to the chamber sometimes.

If you are not using steel, the ejection chart may help lead you to another issue. Misaligned gas block? Some people have had problems with certain ammunition not generating enough gas to properly run the action, like some 7.62X51 NATO ammunition. Since the M&P10 is designed for .308 Winchester ammunition (the hotter round), that may be the problem.

Try to do one thing at a time in order to use the process of elimination. If you do a bunch of things at once and fix the issue, you don't know what the root cause of the issue was.

 

[TexasE]

First off, thanks for all the great info. It is much appreciated.

By the chart, when it runs right, it is in the perfect zone. Between straight out and just forward of my right shoulder.

As to the buffer, the retaining pin works if the buffer is in the correct rotational angle.

From the lube chart supplied I would say i used way too little lube. The bolt required very heavy force to move with the carrier removed. I was not sure what was normal. After this clean up and adding more than just a film to some key pieces things already cycle smoother.
I am shooting factory Winchester FMJ target rounds. NATO brass.

 

[sgtsandman]

Try some .308 rounds and see if you get the same thing, however from your description, it doesn't sound like the ammo is the problem. My M&P10 runs both fine.

There is a thread about the extractor not sitting correctly, in the M&P15 section. I think they were talking about extraction problems as well. Part of the discussion was exploring the possibility of there being contamination in the hole where the ejector is as well. I'm just throwing some ideas out there.

It should look like this:

 

[lrrifleman]

Hello. Please let me qualify my response with the comment that my AR experience is limited to AR15 type rifles.

It sounds more to me that the source of your jamming problem is more your magazine, not the rifle. It sounds like the next round in line jumped past the magazine lips and dislodged to extracted case, causing a wedged jam.

I would suggest that you test each magazine that you have by fully loading the mags and thumbing rounds out of the Mag, noting if any rounds jump the lips. If a round does jump the lips, mark the mag. You should be able to adjust the lips with a pair of needle nose pliers.

If it proves to be a Mag issue, I would be interested in knowing if it was an aftermarket magazine.

 

[sgtsandman]

The M&P10 operates the same as an AR-15, everything is just bigger.

It could be a magazine issue.

 

[MasterTech1960]

Ok, this is not saying what is wrong with your rifle as far as feeding and ejecting but it may help in discovering what may be the problem. Not to mention it may help in the future.

Try to do one thing at a time in order to use the process of elimination. If you do a bunch of things at once and fix the issue, you don't know what the root cause of the issue was.

Hay , mine troughs all my spent brass into a rail mounted Caldwell brass catcher , is that O.K Sorry sgtsandman , I just could not help myself. Great graphics by the way and good advise.

 

[sgtsandman]

I still need to get one of those so I'm not chasing brass.

 

[TexasE]

Hello. Please let me qualify my response with the comment that my AR experience is limited to AR15 type rifles.

It sounds more to me that the source of your jamming problem is more your magazine, not the rifle. It sounds like the next round in line jumped past the magazine lips and dislodged to extracted case, causing a wedged jam.

I would suggest that you test each magazine that you have by fully loading the mags and thumbing rounds out of the Mag, noting if any rounds jump the lips. If a round does jump the lips, mark the mag. You should be able to adjust the lips with a pair of needle nose pliers.

If it proves to be a Mag issue, I would be interested in knowing if it was an aftermarket magazine.

Thank you for your input.
I am using the factory steel mag and a couple of 20 round and 25 round PMAGs. Those are plastic so not adjustable.
Same issue with all mags.
When it jams the spent shell is still in the ejection port and the next bullet is slid forward into the ramp area but still trapped in the mag.
Thanks again.

 

[TexasE]

On a follow up. It has rained the last few days so I took it down again.
I see now that the buffer tube was clocked slightly wrong. The notch in the tube that allows the retaining pin to extend into the tube is not in alignment. It only allows the pin to come up slightly. I am assuming you guys need to depress the pin to release the buffer? I just have to rotate it so one of the flats is at the bottom and it slides right out without depressing the pin. It looks like if I looses the crown nut and aligned the buffer tube it will allow the pin to come up a bit higher.

I also noticed the buffer did ding the upper when. I was able to knock down the nicks with a white stone. The buffer coating/anodizing was also nicked and cleaned up but is now compromised.

After more cleaning, a bit of polishing and good amount of lube it feels like a new gun (it is a new gun, go figure). I do feel lube may be the original issue but I must say, for such a highly regarded rifle I am beginning to have doubts about the assembly process. Both my muzzle brake/flash hider and the buffer tube appear to be installed "out of time". It has led to some damage (mostly cosmetic).
I hope this is the end of it. I will update after next range test.
Thanks again!

 

[sgtsandman]

The pin does need to be depressed to to remove the buffer and spring but it still needs to be retained by the tube.

As far as the lube, all AR rifles are like that. Until they get broken in, they need to be well lubed.

Things not being timed right, that is a different story.

 

[TexasE]

Okay, last update before the range. Again.
I got a tool for the buffer tube nut and loosened it. Centering the tube allowed the pin to extend enough to stop the buffer. I also noticed some marks in the upper. It became clear that the buffer tube was in contact with the upper! So I backed the tube out a turn and re tightened the nut. Now the buffer is retained in all positions AND the take down pin is functional by hand. Two bird one stone? We will see.
Looks like I may have got a Friday afternoon gun but if its just some adjustments..... Cant wait to get back out.
I will update.

 

[MistWolf]

Actually damaged a few unfired rounds as fresh round was wedged under the spent round in the upper. Had to use a tool to push the fresh round back into the mag so I could eject the mag

This is an extraction issue. Either the extractor is out of spec, the spring is weak, or there is some kind of debris hampering function.

Don't bother to poke the round back into the magazine. Just rip the magazine out of the magwell, cycle the action two or three times to clear it and lock the bolt back before inserting the mag

 

[TexasE]

Final update

Great news!
Got out to the range. 120 rounds without a hick-up. Ran flawlessly.
While not dedicating my time to jams I could focus on getting the new Glass dialed in. Quick and easy. Really nice group and then 300m steel. Over and over. What a great rifle. I am converted.
After cleanup I find it is not "dry" this time around and everything is much smoother in operation. It would appear that lube was the primary cause of earlier jams.
Thanks again for the input!

 

[Rugbyreb]

Lube it.

Lube it like you're trying to get an elephant in a Volkswagen. It helped me huge.

Hello. Please let me qualify my response with the comment that my AR experience is limited to AR15 type rifles.

It sounds more to me that the source of your jamming problem is more your magazine, not the rifle. It sounds like the next round in line jumped past the magazine lips and dislodged to extracted case, causing a wedged jam.

I would suggest that you test each magazine that you have by fully loading the mags and thumbing rounds out of the Mag, noting if any rounds jump the lips. If a round does jump the lips, mark the mag. You should be able to adjust the lips with a pair of needle nose pliers.

If it proves to be a Mag issue, I would be interested in knowing if it was an aftermarket magazine.