New Year New Problem

[Sonny Gunny]

Back from the range after installing BABC compensator and I am not sure if a muzzle break has this effect or some other reason.

I did change the gas block to Troy low profile and new handguad and did a function test prior to this trip with no issues.

The bolt will not lock back after last round, tested it with one round in PMAG with same result. This only happened with 147 grain FMJ PMC ammo, yet no problem with the 168 grain OTM Federal...locks back full function. Additionaly, had 2-3 FF and noticed ding on the PMC ammo only, not the American Eagle.

The groupings @ 100 yards were good 0.5 - 1.5" when I focused with the 168 grain (the flyers are rapid shots mainly with the PMC ammo).

I could just use the 168 and be done with it but liked the cheaper 147 PMC and it ran good prior to the break, I just never thought a compensator has an effect like this?

Any thoughts or suggestions would be appreciated...and Happy New Year (I wish ammo prices to fall in 2014)

Footnote: The comp works and it is not loud, the smith could not install it with the supplied crush washer so he used shims, I really don't think that has any bearing but I am new at this.

 

[apiccola]

Sound's like you may not have the new gas block lined up with the gas port on the barrel well or the new gas block may not be seated around the gas port snugly. When you installed the new gas block, did you push it all the way against the boss lip on the barrel or did you leave a gap approximate to the thickness of the original handguard retainer? If you did not leave an appropriate gap, the gas block port may just partially align with the barrel gas port, causing this issue.

 

[Sonny Gunny]

The Gun Smith installed the gas block and he did leave space. After the install of the gas block (less compensator) I went to the range and fired about 100 rounds with the same mix with no issues, which may suggest as you said the gas block got loose when I went for the second time to the range. The funny thing is that it only happens with the 147 vs. 168.

I have no ejection issues matter of fact maybe too much like 5-6 feet away at the 4-5 o'clock position all in one pile.

 

[apiccola]

It's a good practice to re-torque the clamp screws on a new gas block after some range play. The initial heat expansion tends to stretch the threads on the fasteners.

 

[Sonny Gunny]

Hopefully it works, screws were pretty tight in there but I went ahead and torqued them more ... I did not know what value so I stopped a little shy of 20 in-lbs. If I am still having issues next range day I will go back to my local gunsmith.

Thanks again for the input, much appreciated.

 

[Sonny Gunny]

Post range report and visit to smiths (not my usual guy he was out) anyhow... first 80 rounds functioned great ..bolt locks up with authority after last round and just when I was smiling from ear to ear ..the bolt did not lock back, not 168 grain or 147 so mad I just wrapped up my session and off to the smith.

He said that the screws were tight but the problem was my buffer tube its meant for an AR15?? I explained that its S&W proprietary tube and does look similar in length to the AR15.

Please take a look at the attached pics should the other side look like this? and it seems the holes are not the same.

In conclusion, don't mess with what works

 

[apiccola]

Sonny Gunny, your picks are of the gas block/tube not the buffer tube. Was your smith referring to the gas tube? If so, the gas tube diameter is the same for the ar15 and the ar308 models. If your smith is referring to the buffer tube, please confirm whether or not the original buttstock, buffer and buffer spring are still used in your rifle.

 

[Sonny Gunny]

apiccola,

Yes stock spring and buffer and the buttstock is magpul CTR, the smith referred to the buffer as not being an AR10 buffer, he even showed me one from another make half the size but I recall seeing the M&P10 buffer in other pics and it shows similar to AR15 in length. Prior to the troy low profile block I had zero issues with same set-up.

 

[apiccola]

The stock buffer on the MP10 is a standard ar15 carbine buffer. In working with my MP10, I observed the original gas port diameter close to minimum diameter tolerance for an 18" barrel. I ported my gas port to almost .080", which is comparable to the gas port on my DPMS LR308. If the smith confirmed the gas system as airtight with no leaks around the gas block, and there are no apparent impingement of the moving parts, there may be a small restriction caused by some copper or carbon residue at the miniscule gas port. On a lucky chance, such a restriction might sometimes be cleared just by boresnaking the barrel, or by shooting compressed air back through the gas tube and then boresnaking the barrel. Really sorry to hear about the problem you are experiencing with your rifle, and can only imagine your frustration.

 

[Jessie]

Anybody have range reports from a stock M&P 10?
Just curious as to accuracy and function with a stock rifle.
Maybe that's how it was designed?
I'm as guilty as most and have changed mine with handguard, gas block, etc.
Just wondering if people are having the same short stroke, fte problems with stock rifles as those with mods?

 

[azureoval]

Anybody have range reports from a stock M&P 10?
Just curious as to accuracy and function with a stock rifle.
Maybe that's how it was designed?
I'm as guilty as most and have changed mine with handguard, gas block, etc.
Just wondering if people are having the same short stroke, fte problems with stock rifles as those with mods?

I have had FtF issues with mine and the only part that I have changed that maybe could have an effect is the muzzle brake. I switched to a different Buttstock,Grip and Handguard but never touched the gas block.
The first trip to the range I only had the stock 10 round (Cali special) ASC metal mag. I was shooting S&B and PMC 147's . I would get failure to load 7-8 times a mag. Sometimes 2 rounds would be jammed in there and would have to eject the mag and unstick everything. I put about a 100 rounds through
that day.
The second trip I had some new Magpul 10 rounders and the first 3 mags went through without a hitch. I thought I had the problem licked with the new mags. Then the next mag had the same problems and it continued till I wrapped it up for the day and shot my M&P15 that works. I added Herters and Federal ammo to the mix this time also. All were equally jamtastic.
I hope that this is just a break-in issue and will try to pump some more rounds through it soon. Maybe alter how I lube the gun and see if that has an effect.

 

[apiccola]

I had accuracy issues with my MP10. Even shot groupings from a quality bench rest were very erratic and exceeded 8" from 100 meters in some cases. This problem has not reoccurred since I've changed handguards to the Magpul MOE. I had no failure to fire or short stroking issues with the original MP10 configuration. I shot two 50 round boxes of CBC 168 grain BTHP before I started with buffer/gas system modifications.

 

[rojodiablo]

Anybody have range reports from a stock M&P 10?
Just curious as to accuracy and function with a stock rifle.
Maybe that's how it was designed?
I'm as guilty as most and have changed mine with handguard, gas block, etc.
Just wondering if people are having the same short stroke, fte problems with stock rifles as those with mods?

There have been issues with FTF, FTE on these rifles from day 1. The buffer, gas pressure are not quite correct in many cases, and the rifles need some tuning. Accuracy on those I have worked on was good, so no problems from that aspect from what I have seen.
Primarily, the buffer has needed about 1/4 to 3/8oz of weight added to it to get the rifles to feed dependably.

As a secondary measure, guys are having more success with enlarging the gas port hole a little. This has helped the rifles become much less picky eaters, and alleviated this kind of issue where the rifle likes one weight/ type of ammo but will not reliably function with another.

And it's frustrating, because PMC is not on the friendly ammo list for these rifles..... and that sucks, because PMC is making really good ammo.

 

[cb4017]

Anybody have range reports from a stock M&P 10?
Just curious as to accuracy and function with a stock rifle.
Maybe that's how it was designed?
I'm as guilty as most and have changed mine with handguard, gas block, etc.
Just wondering if people are having the same short stroke, fte problems with stock rifles as those with mods?

Here is a link to my initial review.
http://smith-wessonforum.com/smith-wesson-m-p10-rifles/305881-m-p-10-range-review.html

 

[Sonny Gunny]

It's frustrating but I don't give up that easily. I have on order a DA7 Adjustable Gas Block DA7 Adjustable Gas Block, I have read good reviews on the product and although I will never run suppressed (lovely Cali) I will tinker around with pressure and hopefully resolves my issue, just replacing the Troy with this might do it.

 

[apiccola]

Rojodiablo, you are spot on. S&W should consider taking steps to refine the balance of the gas system design, including augmenting the buffer weight as may be necessary. Although I didn't experience the fast cycle issue in trial when my rifle was stock (but that was only for 100 rounds), I did sense that issues were on the horizon if I didn't take on some enhancements ... and that's not the feeling a consumer should have with a $1500 investment.

 

[apiccola]

Sonny Gunny, I have a spare 4.5oz carbine buffer that I would be more that happy to mail to you. It may help with your issue. If you want it, shoot me a mailing address via private messaging.

 

[Sonny Gunny]

Thank you brother for the offer and suggestion, I have Spike's ST-T2 (4.05oz) in my M&P 15 that I will try-out next range day (all this range testing is depleting my ammo, and 308 is not cheap).

 

[Sonny Gunny]

apiccola,

Just wanted to update you as I am back from the range, the heavier buffer actually was worsening my problem, everything functions ok as soon as the barrel heats up (about 40 rounds or so) bcg will not lock back after last round, anyhow going tomorrow to my local gunsmith and maybe he can help.

 

[apiccola]

I hope your smith is able to muster the solution. I just have a sneaking suspicion that there is a mild gas leak or restriction ... wouldn't think it would be port sizing based on your setup. Although, in another thread, a fellow remarked that he thought his gas port was about .040", which is about the size of a sewing needle ... I would definitely consider that a manufacturing defect, but unclear on the probability that would really happen on the basis of the tooling used in manufacturing the barrel.