Range Report - M&P-10 Sport - Problems.

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Well, I'm a bit disappointed. The big M&P-10 Sport didn't want to cooperate with me last night. Field-stripped and cleaned (not an extreme, thorough cleaning, I admit, because it wasn't dirty - just got most of the preservative oil off, that was on it). The patch I ran through the barrel did come out with some carbon, so, I reckon they test-fired it before leaving the factory. Lubed with synthetic motor oil (I think it was some Pennzoil Platinum 10W-30 I had left over from the car - I honestly can't remember, because I keep it in a syringe. The only other thing it could be is the M1-EP 5W-30 I use in the truck. Anyway, I thought I'd lubed it pretty generously. More on that later... Got to the range, put the scope on, and started shooting with some Federal XM80C (Lake City 149g, 7.62x51mm). It was grouping well at 25 yards - definitely under 2" - then it jammed. What it did to the case of the cartridge. It also set the bullet back in the case a hair. Had to remove mag to clear the jam. Got it cleared, chambered another round, fired, pulled trigger again, CLICK. Removed mag and looked. Bolt had failed to strip a fresh round from the magazine. And I could see score marks across the top of the cartridge case, where, presumably, the bolt rode over top of the round and scratched it: It did this kind of thing a few more times, and, once, I couldn't even pull the charging handle back without removing the mag and pulling really hard. So, I decided to take it upstairs and let one of the old guys who works there look at it. We field-stripped it and he said everything looked OK, but that maybe it needed more lube. He handed me some CLP called "Clenzoil", I think (it was pretty thin stuff). We lubed everything generously. Took it back down to the range and tried again with some different ammo - this time, Aguila 150g 7.62x51mm. Same problems. FTFs. At this point I didn't want to mess with it anymore, so I got my Dan Wesson Heritage 1911 out. That saved my range trip - I love that pistol. Never a single malfuction. Right now, the plan is to clean and lube again, even though it's pretty wet at the moment and only has about 15 rounds, or less, through it, and see if I can get my hands on a couple of different magazines to try. I also have a box of Federal .308 180g hunting rounds. Those should be a little hotter than that milsurp 7.62 stuff. So I'll try that. But, IMO, this thing should handle 7.62 NATO stuff just fine. I'm also going to call Smith & Wesson tomorrow and let them know what happened and see if they've been hearing of this kind of thing, with these rifles, because I know they've sold a bunch of them. Also going to ask them if they'll send me a different mag. It came with one 20-round PMAG. Those are usually GTG, so, I dunno. I haven't had a single malfunction with my Colt 6920. But, then, it's a different animal. Any ideas?
 

OVERKILL

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It should feed, if it requires the Exxon Valdez spilled in the BCG to grab a round there's something else going on with the gun. I'd take it to a smith at this point or send it back to S&W.
 

john_pifer

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Originally Posted By: OVERKILL
It should feed, if it requires the Exxon Valdez spilled in the BCG to grab a round there's something else going on with the gun. I'd take it to a smith at this point or send it back to S&W.
LOL. Agreed. Even the manual says to just use a cloth moistened with oil to lube internal parts. I actually would put a drop of oil with my syringe, then work it over the parts with my fingers. Just like I did with the 6920 with zero problems. There's a pretty good gunsmith at the range where I go (Guns & Leather, Greenbrier, TN), so, I'm going to ask his opinion. He's really friendly and cool about answering questions, etc. I don't want to have to spend money, though. I don't think I should have to, after buying a brand-new rifle. If, after cleaning and lubing again, trying a couple of different mags, different ammo, and the same thing happens again, it's going to Massachusetts.
 

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Yeah, try a different magazine ... maybe a different brand. Any sharp burrs on the bottom half of the chamber entrance?
 

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That sucks... Doubt it's the magazine - I've never once had an issue with a Magpul. Short-stroking. Generally, that's a lack of gas pressure (or lack of lube, which you've ruled out). Any chance the gas tube is plugged up or bent from the manufacturing process? Are the gaps in the gas rings on the bolt still staggered/offset?
 
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I'd try a different magazine - did you load it back to 30 each time? Tap the rounds back after loading? I've had followers get stuck. Could be a weak buffer spring, or as noted above, the gas rings on the bolt.
 

john_pifer

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Originally Posted By: ZeeOSix
Yeah, try a different magazine ... maybe a different brand. Any sharp burrs on the bottom half of the chamber entrance?
I'll check when I get a chance and report back.
 

john_pifer

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Originally Posted By: Astro14
That sucks... Doubt it's the magazine - I've never once had an issue with a Magpul. Short-stroking. Generally, that's a lack of gas pressure (or lack of lube, which you've ruled out). Any chance the gas tube is plugged up or bent from the manufacturing process? Are the gaps in the gas rings on the bolt still staggered/offset?
I kinda agree with you about the magazine. Magpul seems to have their mags pretty sorted. And if they didn't, I doubt S&W would provide that brand with their guns. I made sure the gas rings were staggered each time I reassembled the BCG. How would I check the gas tube for obstructions? Guess I could take the handguard off and see if it looks bent or anything.
 

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Originally Posted By: rooflessVW
I'd try a different magazine - did you load it back to 30 each time? Tap the rounds back after loading? I've had followers get stuck. Could be a weak buffer spring, or as noted above, the gas rings on the bolt.
I did load them back to 20 (max) each time. I didn't tap them, but I think I had the rounds set all the way back. I made sure I did. I forgot to mention that when I finally came to the end of the magazine, the bolt failed to lock back.
 

john_pifer

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Originally Posted By: rooflessVW
Just to be clear: this happened with multiple magazines?
No. This was only with the magazine that came with the rifle. The range where I went only had one AR-10 magazine and it was identical to the one I already had, I think.
 

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A reliable AR-10 is a rare thing and I have not heard good things about the S&W's either. I know that isn't really helpful but it is the truth. Although you shouldn't have to, try different mags and see what that does.
 

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Originally Posted By: john_pifer
Originally Posted By: rooflessVW
I'd try a different magazine - did you load it back to 30 each time? Tap the rounds back after loading? I've had followers get stuck. Could be a weak buffer spring, or as noted above, the gas rings on the bolt.
I did load them back to 20 (max) each time. I didn't tap them, but I think I had the rounds set all the way back. I made sure I did. I forgot to mention that when I finally came to the end of the magazine, the bolt failed to lock back.
Bolt failing to lock back is consistent with the rest of the malfunctions - the bolt is short stroking (not going far enough back). As I mentioned, that's an "under-gassed" problem, usually. I would contact S&W this morning and ask what troubleshooting steps they recommend. That feed problem isn't a magazine issue, the magazine pressed the round up when it was supposed to, but the bolt wasn't far enough back for it to properly feed. The times that it fails to load, it's really short-stroking, and the round stays in the magazine. You can try another magazine (in fact, I recommend having several magazines for every firearm) but I don't think you'll get a different result. While my DPMS is made by a different company, it's been completely reliable, once I figured out that it doesn't like light oils, like Rem-oil (I know, ironic). Even when it was acting up (same symptoms, short-stroking, and feeding just like your picture), a couple drops of oil on the bolt would have it running again. It may be that my DPMS is also "under-gassed" a bit, but as long as it's well lubricated, there is enough gas pressure to cycle everything fully... Good Luck!
 
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Originally Posted By: john_pifer
How would I check the gas tube for obstructions?
Pull the BCG out and try to run a long pipe cleaner, or even a stiff piece of wire down the length of it. (A cut off straight section of coat hanger would work well). It should pass freely all the way from the back of the chamber to the gas block. You also might want to make sure the gas port in the barrel is fully open, and isn't obstructed with a burr of some type. (That would require a look with a bore scope). And I would for certain try some different magazines. While Mag-Pul has a good reputation, they're not infallible. Also try some hotter .308 Winchester ammunition. 7.62 X 51 is not loaded to the same pressure as a lot of commercial .308 is. (It is just the opposite of .223 vs. 5.56 MM NATO. 5.56 is typically loaded hotter than .223). If after trying some different magazines and ammo, (and don't fill them to capacity. Just 3 or 4 rounds to start out with), and assuring yourself the gas system isn't obstructed in any way, then it would appear your only recourse is to send it back. I'm betting if it is fully cycling with hot enough ammo, and has a different magazine, it will run. From everything you are saying, it sounds like the ammo is too weak, and causing it to short cycle. "The Winchester .308 cartridges are typically loaded to higher pressures than 7.62×51mm NATO cartridges." https://en.wikipedia.org/wiki/7.62%C3%9751mm_NATO
 
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As far as ammo, I would give some commercial heavy bullet weight hunting .308 Winchester a try. (180+ grain). The reason is the heavier the bullet, the more slower burning powder it will be loaded with. This will increase the gas pressure when the action cycles. You have to remember that Mil-Spec 7.62 X 51 MM ammo was specified to be pressure curved for the M-14. That Garand action was / is very sensitive to operating pressure. It is why there is specific .30 caliber ammunition made today just for the Garand and M1-A. If these actions are exposed to too much operating pressure, they can bend op rods, and cause damage to the rifle. So medium weight bullets, (147 to 165 grain), loaded with mid range burn rate powder is what these rifles require. The AR platform .308 rifles are nowhere near as ammo sensitive, because they employ a direct impingement gas system. Which is far more forgiving in regards to the pressure curve it operates at. Many operate best at a higher pressure curve. I'm willing to bet yours is one of them. Anyway, it's a cheap, easy place to start. Here is some more information on the difference between the 7.62 X 51 MM NATO vs. the .308 Winchester. http://www.thefirearmblog.com/blog/2007/09/03/308-winchester-vs-762x51-nato/ "The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62×51 max is 50,000 psi."
 
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Don’t **** around with it, you paid for a gun that works, not one you should have to tinker with outta the box. Pack it up, take it to the shop you bought it from and have them send it back to S&W. Let them deal with it. Welcome to the world of the .308 AR platform.
 
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Originally Posted By: ROLEXrifleman
Don’t dick around with it, you paid for a gun that works, not one you should have to tinker with outta the box. Pack it up, take it to the shop you bought it from and have them send it back to S&W. Let them deal with it. Welcome to the world of the .308 AR platform.
While that all sounds good, the fact is the gun was test fired before it left the factory. Which make the issue most likely ammo or magazine related. It would be worth it to at least try it with other ammunition and magazines before going through all of the hassle of sending it back.
 

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Originally Posted By: john_pifer
I forgot to mention that when I finally came to the end of the magazine, the bolt failed to lock back.
Yep, sounds like the bolt isn't traveling all the way back at times. Could be the ammo (under pressure), or could be some intermittent mechanical friction going on. I'd pull back the bolt by hand slowly many times and see if you can feel it hanging up at all throughout the stroke.
 

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Thanks for the suggestions, advice, and info. Astro, your hypothesis seems very likely to me. The symptoms seem consistent with a short-stroking situation, and not a magazine issue. It could be the 7.62x51mm M80 ammo. If that's the case, I'd be disappointed, as I'd expect any semi-auto rifle chambered in either .308 (as this rifle is) or 7.62 NATO, to run Lake City ball ammo. (I also tried Aguila 150g 7.62, which is probably about the same as the Lake City.) But then there's also the issue where it "locked up" and I wasn't able to pull the charging handle back until I removed the magazine. At that time, the bolt was closed. I don't know what was hanging up. If it happens again, and I have to send it in, I'll definitely include a detailed written description of that issue, as well. I'm off tomorrow, so I'll clean and lube the rifle again, and take it back to the range and try that .308 180g Federal hunting ammo I have and see if that makes any difference. I called S&W yesterday, and the guy who answered the phone didn't really provide any specific or super-helpful information. All he said was, "It sounds like you have multiple issues going on; we'll email you a shipping label. Send it in and we'll get it fixed for you." He did agree that it would be reasonable to take the rifle back to the range and try some different ammo. So, we'll see what happens tomorrow.
 

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Originally Posted By: john_pifer
Thanks for the suggestions, advice, and info. Astro, your hypothesis seems very likely to me. The symptoms seem consistent with a short-stroking situation, and not a magazine issue. It could be the 7.62x51mm M80 ammo. If that's the case, I'd be disappointed, as I'd expect any semi-auto rifle chambered in either .308 (as this rifle is) or 7.62 NATO, to run Lake City ball ammo. (I also tried Aguila 150g 7.62, which is probably about the same as the Lake City.) But then there's also the issue where it "locked up" and I wasn't able to pull the charging handle back until I removed the magazine. At that time, the bolt was closed. I don't know what was hanging up. If it happens again, and I have to send it in, I'll definitely include a detailed written description of that issue, as well. I'm off tomorrow, so I'll clean and lube the rifle again, and take it back to the range and try that .308 180g Federal hunting ammo I have and see if that makes any difference. I called S&W yesterday, and the guy who answered the phone didn't really provide any specific or super-helpful information. All he said was, "It sounds like you have multiple issues going on; we'll email you a shipping label. Send it in and we'll get it fixed for you." He did agree that it would be reasonable to take the rifle back to the range and try some different ammo. So, we'll see what happens tomorrow.
Make certain that the gas tube is free of obstructions, I would just hose it out with gun scrubber and chase it with a pipe cleaner. Clean it and lube it (generously). Get a new magazine (even though I think it unlikely). Try the new ammo. But even if it works with the heavier ammo, I would still be unhappy. The rifle should work with M80 ball rounds. That's common (and relatively cheap) ammo in the market and it's about all that I shoot from my rifle. Please report back.
 
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