AR Sponsor
Posted: 11/28/2008 7:39:06 AM EDT
|
I took my brand new M&P15X to the range two weeks ago to start breaking it in (first range trip). I took a variety of brand new D&H mags, used Adventure Line & Colt mags along with an ammo can full of fresh Wolf 55gr FMJ.
The rifle wouldn't cycle at first so I tried a bunch of different magazines. It started to also FTF. I stripped the rifle at the range and hosed down the inside of the upper with CLP. I wiped out the excess and try to run the rifle again. Same problems: * Would not pick up a round out of the mag, but it cycled enough to reset the hammer. * Would strip a round, but not fully seat it in the chamber (would stop with the round 1/2 out of the mag and starting to feed into the chamber). I took the rifle home - cleaned and lubed it. I also stripped, and cleaned the mags. I just returned from the range. I took the problem M&P and an ArmaLite M15. I had the exact same problems with the M&P, but the ArmaLite had zero problems with the exact same ammo and mags. I would take the mag out of the M&P after it malf'd (every round) and would stick it in the ArmaLite. The ArmaLite would run the entire mag without any problems. Has anyone else had these problems? If so, what did you do to fix it? |
|
Sounds like short-stroking. A lack of sufficient gas to fully cycle the action.
ETA: Do you have a pic of the rifle? Here’s a thread where the OP had a similar problem. It might be a start to read through it. http://www.ar15.com/forums/topic.html?b=3&f=118&t=407744 |
|
Quoted:
What are you looking for in a pic? Sometimes it helps to have a picture, which can be better than a description of the weapon. I’m looking for accessories or modifications that might affect gas flow. Also any recent maintenance you might have performed. |
|
Quoted:
Quoted:
What are you looking for in a pic? Sometimes it helps to have a picture, which can be better than a description of the weapon. I’m looking for accessories or modifications that might affect gas flow. Also any recent maintenance you might have performed. Let me know if you need additional pics, and thanks for the help. |
|
I don’t think additional pics will be necessary. Thanks for posting them though.
My first concern when folks start posting about new weapons which exhibit symptoms of short stroking, is modifications done to the weapon which could affect gas flow. Standard Front Sight Bases removed and replaced with clamp-on gas blocks or BUISs, which are not aligned properly with the barrel gas port causing gas system restrictions. Barrels removed to facilitate installation of a Free-Float hand guard, where the barrel nut teeth are not correctly aligned causing the gas tube to bind on the carriers gas key. Stocks removed and replaced where incorrect buffer springs are installed, or even parts left in shipping bags, stuffed down inside the receiver extension by the shipper/dealer, and overlooked by the end installer. These are all but a few possibilities. Read through the post I tacked above for starters. Go through my troubleshooting list as well as Paul from Bravo Companies list. That should get you started. Quib |
|
Quoted:
I don’t think additional pics will be necessary. Thanks for posting them though. My first concern when folks start posting about new weapons which exhibit symptoms of short stroking, is modifications done to the weapon which could affect gas flow. Standard Front Sight Bases removed and replaced with clamp-on gas blocks or BUISs, which are not aligned properly with the barrel gas port causing gas system restrictions. Barrels removed to facilitate installation of a Free-Float hand guard, where the barrel nut teeth are not correctly aligned causing the gas tube to bind on the carriers gas key. Stocks removed and replaced where incorrect buffer springs are installed, or even parts left in shipping bags, stuffed down inside the receiver extension by the shipper/dealer, and overlooked by the end installer. These are all but a few possibilities. Read through the post I tacked above for starters. Go through my troubleshooting list as well as Paul from Bravo Companies list. That should get you started. Quib Quib, Thanks - the rifle is bone stock except for accessories (KAC VFG, KAC RC's, Aimpoint & TLR2, BHI Snap Shoot Sling). I read thru the link, and have the rifle stripped. Here's what I see: 1) The gas rings are staggered. 2) The BCG drops right in (not binding). 3) The gas tube shows no signs of "bleed" at the FSB. 4) The gas key is properly staked. 5) A pipe cleaner makes it thru the key into the carrier. 6) The rec. extension is clean inside and without burrs. 7) The barrel nut isn't binding the gas tube. Any thoughts? 
|
| Sounds like everything is as it should be, but it is definitely short stroking. The only thing I can think it could be after reading above would be the gas port in the barrel may be too small. You could start exchanging parts with the Armalite until you figure it out, starting with the buffer and spring. I really don't think it is the bolt and bolt carrier, but make sure that is lubed really good, don't wipe excess off of that. |
|
Since you have two rifles, you might be able to isolate the problem further.
Have you tried to swap uppers to see if the same thing happens with the same upper/lower? That would be the way I would isolate the problem to the upper or lower. If it seems like the upper is the culprit, swap the BCG and charging handle. If the problem moves with the BCG and charging handle, then swap one back. The idea is to isolate the problem to the most discrete component you can through gross component substitution. When you have narrowed it down to the smallest assembly you can; then decide what your options are. In your case, if the rifle is still in warranty, contact S&W. If it's not, then either fix it yourself or get a good armorer/gunsmith involved. Tom (Tachyon) |
|
Quoted:
Quoted:
I don’t think additional pics will be necessary. Thanks for posting them though. My first concern when folks start posting about new weapons which exhibit symptoms of short stroking, is modifications done to the weapon which could affect gas flow. Standard Front Sight Bases removed and replaced with clamp-on gas blocks or BUISs, which are not aligned properly with the barrel gas port causing gas system restrictions. Barrels removed to facilitate installation of a Free-Float hand guard, where the barrel nut teeth are not correctly aligned causing the gas tube to bind on the carriers gas key. Stocks removed and replaced where incorrect buffer springs are installed, or even parts left in shipping bags, stuffed down inside the receiver extension by the shipper/dealer, and overlooked by the end installer. These are all but a few possibilities. Read through the post I tacked above for starters. Go through my troubleshooting list as well as Paul from Bravo Companies list. That should get you started. Quib Quib, Thanks - the rifle is bone stock except for accessories (KAC VFG, KAC RC's, Aimpoint & TLR2, BHI Snap Shoot Sling). I read thru the link, and have the rifle stripped. Here's what I see: 1) The gas rings are staggered. 2) The BCG drops right in (not binding). 3) The gas tube shows no signs of "bleed" at the FSB. 4) The gas key is properly staked. 5) A pipe cleaner makes it thru the key into the carrier. 6) The rec. extension is clean inside and without burrs. 7) The barrel nut isn't binding the gas tube. Any thoughts?
If everything looks good thus far, it could be the Wolf ammo. Clean the rifle well, and get some better quality ammo. Before you head out to the range, lube things up good. Let us know how it goes the second time out. |
AR Sponsor