Another MP10 with Problems

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southpaw187

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Bought this MP-10 about a year ago. Stripped it down, installed SLR gas block and SLR rail. Dimpled the barrel and used gas block alignment jig so that is perfectly installed. Gun has frequent failures with FGMM 175 SMK rounds. This is my go to round, I need it to reliably function. Buffer tube, spring and buffer are stock. Ejection is pretty weak with cases landing around 4:00 about 5-6' away. Failures include: Improper feeding of subsequent round after firing (a nose up jam) and also short stroking causing failure of bolt to strip another round out of the magazine after firing, causing the next trigger pull to be a click. So then the thing is a damn bolt gun. I am going to call Smith and see what they say. But I am prepared to bore the gas port open if SW won't help me, in order to get a little more gas into the system because that sure seems to be the culprit. Any suggestions or other trouble shooting tips are welcome. I don't think there is a lighter buffer to try, but maybe a weaker spring? Thanks.
 
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Did you shoot the rifle before you upgraded the gas block? If so and it ran fine then, have you pulled the gas block off to look for an obstruction in the new gas block? Like a burr or something blocking the port? Also check your gas tube in case something from the new block got blown into there. They sell gas tube cleaners that look like long pipe cleaners that you could use to clear the tube out if you find something.


At one point, S&W had a policy that if you upgraded your rifle, your warranty would not be honored. That has changed since then but I do not remember the particulars as far as what limitations, if any, now exist.


EDIT: There is a post similar to yours in here that is recent that may apply to you. You haven't mention what version of M&P10 you have, so it may or may not apply but it is another thing to look at if everything else looks good.
 
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sgtsandman said:
Did you shoot the rifle before you upgraded the gas block? If so and it ran fine then, have you pulled the gas block off to look for an obstruction in the new gas block? Like a burr or something blocking the port? Also check your gas tube in case something from the new block got blown into there. They sell gas tube cleaners that look like long pipe cleaners that you could use to clear the tube out if you find something.


At one point, S&W had a policy that if you upgraded your rifle, your warranty would not be honored. That has changed since then but I do not remember the particulars as far as what limitations, if any, now exist.


EDIT: There is a post similar to yours in here that is recent that may apply to you. You haven't mention what version of M&P10 you have, so it may or may not apply but it is another thing to look at if everything else looks good.
Click to expand...

Good advice sir. Mine is the 308. No I did not shoot before dissassembly, that was a mistake. I can dissassemble and inspect. If everything is clean, I will call SW. If they wont honor the warranty I will go from there.
 
southpaw187 said:
Good advice sir. Mine is the 308. No I did not shoot before dissassembly, that was a mistake. I can dissassemble and inspect. If everything is clean, I will call SW. If they wont honor the warranty I will go from there.
Click to expand...



There is a M&P10 with an 18” barrel and the Sport model with a 16” barrel. I think everything else is the same same between the models. Barrel length may or may not have an effect on what the gas port size needs to be and how sensitive the rifle might be with different rounds and the shorter barrel. Two inches may have an effect on gas pressure dwell time in the barrel.


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Hey guys, a quick update on my plan here, before I go pulling the upper fully apart to mess with the gas port, which pains me to even think about, I am going to try a different spring. The spring the gun came with is 13" long and has 34 coils, and from what I can tell, this is a rifle length spring. I have a DPMS 308 Carbine spring, that is 11.5" long and has 28 coils, and I am hoping this will fix my problem.

My theory is this: Gun is short stroking as evidenced by weak ejection and lack of scooping up the next round; however the trigger is being reset. That means more gas, or less spring/buffer resistance is needed to fully cycle the rifle. So I am going the spring route.

If this does not work, there really is no lighter spring or buffer to work with, so that would mean dickering with the gas port.

On another note, I had to order a new rear take down pin because mine will easily pull right out of the rifle, what a joke.

I will let you guys know if I am successful with this spring.
 
Success!! The DPMS carbine spring was the ticket. Excellent ejection pattern at 3-5 yds, 4’clock. Fires everything i fed it. 145 to 175 grain both steel amd brass cased, from russian steel to gold medal match. Probably ran 8 different factory loads. Now, I am going to try out a JP Silent captured spring system, will let you all know how it goes.
 
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southpaw187 said:
Mine has the 18” barrel
Click to expand...

My new 16" M&P-10 sport that I picked up last month is doing the exact same BS. I sent it back to S&W after they said they knew what the problem was. They told me to not expect to see my brand new rifle for 2 months. Total nonsense. BTW I tested my 308 before changing a single item just in case something like this happened and it did. My 223 M&P sport I got at the same time ran perfectly before and after swapping the gas block etc. etc. I am now wishing I would have skipped the 308. I am setting them up identical when I eventually get the 308 back.
 
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Picking up my new M&P10 18” today. Hopefully this short cycling issue has been resolved at the manufacturing level.
 
After reading these posts, I’m not going to modify mine. I think my nearly trouble free stock m&p 10 operates just fine.
 
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