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S&W M&P 15 single shot cont.

pietro75
Continued from topic" Reviews on S&W M&P 15"

Bought a New S&W M&P 15 shot first 1000 rnds. good. Started having feeding problems, I chamber a round,fire it,the shell ejects and the bolt closes w/o chambering another round.

I have stripped the gun and the gas system is imaculate. I was shooting wolf ammo for the first 1000 rnds.

I believe the bolt is not going back all the way. I put one round in a magazine, loaded it, charged the bolt, shot the would be last round. The bolt ejects the empty cartridge and hangs up on the magazine. When I pull out the magazine, the bolt slams forward.

Thanks in advance for all help!
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Comments

7 comments

Date Votes
  • Mossbergboogie
    Try a different mag and see where that gets you.
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  • Txs
    First thing I'd do is try several different mags.

    If the problem persists, you possibly have insufficient gas pressure due to leakage somewhere.

    First check that the bolt carrier's gas key is tight. Visually inspect the staking on the key's bolts to see if they've rotated. If nothing is apparent, grab the key and try to twist it. If the bolts are no longer staked properly or any looseness at all with the key is observed you've found your problem.

    If the key is tight, remove the handguards and inspect the entire gas tube for looseness. As long as it's tight, a small amount of discoloration from leakage where the tube enters the front sight base is normal.

    It's doubtful this would be an issue on a newer rifle, but check the gas rings. Strip it down to just the carrier assembly, then insert the bolt. Tip the carrier with the bolt pointing downwards. It should not fall free from the carrier due to gravity alone.

    Don't fret that the alignment of the gaps on your gas rings could be the problem. Contrary to what many were taught during military instruction this isn't an issue.

    All this being said, I saw a new M&P15 awhile back that developed an issue similar to what you're seeing after several hundred rounds. Turned out that the rear of the gas tube was tweaked slightly and not lining up properly with the gas key. All it took was slight bending of the tube to fix.

    To check this, first remove the bolt assembly from the carrier. Push the carrier all the way into into the receiver slowly. If the key is binding on the tube you'll feel it balk when it reaches this point.
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  • dppatrol
    i had the same problem once,it turned out the buffer tube was tweaked(bent)so the carrier wasnt travelling all the way back.i replaced it and that was it.the magazine is often the culprit,also is there an issue with the bolt release?
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  • midnightrunpaintballer
    my armalite did the same thing for the first 500 rounds. i was also using wolf. i lubed the crap outta the bolt carrier and now it runs fine. even with wolf.
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  • pietro75
    I think I figured it out, I took my bore light and inspected where the bolt seats in the bolt assembly and there was major carbon build up around the hole the firing pin comes through and where gas shoots up into the key. So much carbon that I don't believe the bolt was able to seat back far enough letting too much gas out in the bolt assembly/carrier and not allowing enough pressure for a cycle. After scraping/dremel/gunscrubber. I got it cleaned out and upon firing last round the bolt holds open. I haven't been to the range to see if repeated fire is functioning porperly.
    You guys think that it is the solely wolf ammo? I never did scrape out this part of the gun before. Is this a common build up spot? (obiously is) But is it something you AR guys were already aware of, since I did say the gas system was imaculate, I did overlook this part. Thanks for all the comments.
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  • perry shooter
    As I stated on my post to your question when you first asked .IMHO dirty gas system can happen more often with Dirty Cheap non U.S. made ammo Wolf is one of those. Glad you found problem. A clean well lubed gun is a happy gun no matter if Handgun Rifle or Shotgun.
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  • Txs
    quote:Originally posted by pietro75
    I think I figured it out,I took my bore light and inspected where the bolt seats in the bolt assembly and there was major carbon build up around the hole the firing pin comes through and where gas shoots up into the key. So much carbon that I don't believe the bolt was able to seat back far enough letting too much gas out in the bolt assembly/carrier and not allowing enough pressure for a cycle.An AR's bolt doesn't come close to seating against the inside of the carrier in this area. The tolerance here is along the lines of 1/4 in. or more.

    Rearward travel of your bolt is limited by the cam pin.

    One way or another, if your bolt does not seat completely the the rifle is designed not to fire. This is to prevent firing out of battery and blowing your receiver up.

    If Wolf ammo is the cause of your problems it would be due to buidup inside the gas tube, but do NOT attempt to clean it by inserting any sort of object. Spray a liberal amount of high pressure solvent (GunScrubber or non-chlorinated brake cleaner) directly into the tube from the rear, allowing it to flow out into the bore. After wiping the bore, fire a magazine of good quality ammo through it and let those ~50,000 lbs. of pressure they generate help you out.
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