View Full Version : FTE problem today, What you guys think? Update in OP.
FailureDrill-P099
04-21-12, 16:12
Had a shooting class today and one of the guys with me was having a problem with is AR. We tried to do a field diagnosis but came up empty. He was shooting a new M&P 15. He stated when he bought it he took it out and it had problems.
It would fire one round, fail to eject casing. As I was watching, the bolt did not even seam to cycle. we tried different ammo, different mags, I replaced the buffer and spring, took the bolt carrier group all the way down and found no issues. The bolt, bolt carrier, gas rings everything looked GTG.
I then noticed the hammer pin was coming out and the hammer was not working properly. We tapped the pin back in. I put my 6920 lower on his upper and still a no go. It was getting harder to charge as well.
Only thing I could think of at that point was to tell him to send it back to S&W as it might be a chamber or gas system issue. What you guys think, is there anything else I missed.
Update, well my friend said he was confident in me diving in to the rifle a little more. So I took it down and looks like we solved the issue. Gas block. Thanks for the help guys.
The retaining screws on bottom were very loose.
http://i300.photobucket.com/albums/nn40/dunklarsen/IMG_4976.jpg
http://i300.photobucket.com/albums/nn40/dunklarsen/IMG_4977.jpg
Moved it back and put loctie on the screws.
http://i300.photobucket.com/albums/nn40/dunklarsen/IMG_4978.jpg
http://i300.photobucket.com/albums/nn40/dunklarsen/IMG_4979.jpg
Had a shooting class today and one of the guys with me was having a problem with is AR. We tried to do a field diagnosis but came up empty. He was shooting a new M&P 15. He stated when he bought it he took it out and it had problems.
It would fire one round, fail to eject casing. As I was watching, the bolt did not even seam to cycle. we tried different ammo, different mags, I replaced the buffer and spring, took the bolt carrier group all the way down and found no issues. The bolt, bolt carrier, gas rings everything looked GTG.
I then noticed the hammer pin was coming out and the hammer was not working properly. We tapped the pin back in. I put my 6920 lower on his upper and still a no go. It was getting harder to charge as well.
Only thing I could think of at that point was to tell him to send it back to S&W as it might be a chamber or gas system issue. What you guys think, is there anything else I missed.
If the BCG isn't moving at all, then the gas tube might be installed upside down.
C4
Battle*Hound
04-21-12, 17:29
If the BCG isn't moving at all, then the gas tube might be installed upside down.
C4
Good Call
Did he even test fire before the class or did he buy it and take it to the class? In other words is this a new problem or did it just start at the class?
FailureDrill-P099
04-21-12, 17:42
He new he had this problem. He brought a back up. He thought it was just the ammo he was shooting and it was new.
Always short stroke test malfunctioning rifles.
Blankwaffe
04-22-12, 00:01
^ Elaborate please.
See the quote below.
Try some known good mags. Known good meaning that they can lock the bolt back when empty on all other ARs.
Use the more powerful quality ammo.
Load several mags with 1 round each and fire the one round. Did it lock back?
If it did then load 2 rounds per mag, attempt to fire both rounds, did the second round feed and fire?
If it doesn't work with this try a known good bolt carrier (one that works well in another rifle). Use your own bolt, cam pin, firing pin and firing pin retaining pin. Then try the 1 round per mag test again. If this other carrier makes the gun work then it's leaking at the carrier key.
Even more detailed information available on the subject by way of forum search function.
If you figure out why the bolt is jamming and still short strokes I'd look into checking the gas port size/ make sure the gas block is lined uped.
^ Elaborate please.
I'll elaborate a little more. Start with known good magazines and ammunition.
Load one round into a magazine and load your rifle.
Point the rifle in a safe direction and holding it as loosely as possible, preferably by the pistol grip only, fire the round.
Did the bolt lock back with the bolt face behind the bolt catch?
If it did repeat several times.
If it didn't fully lock back repeat the test firing but this time push in and hold the bolt catch button when you fire.
If the bolt doesn't lock back you might have insufficient gas.
Shortstroke/Underfunction can manifest as FtEx and FtEj.
Troubleshooting Checklist (https://docs.google.com/document/d/1qoWI_7RUgeCjN8kBeCc2L3oGZUeNHu948xvqRF1aMMU/edit)
FailureDrill, did you run a pipe cleaner through the carrier key into the carrier bore?
Did anyone check the gas key for tightness?
KyAKGuy
FailureDrill-P099
04-22-12, 05:51
Yes I checked most of this out. He had a free float rail system and I did not have the tools to take it off and get to gas tube. I was really stumped on this one. Everything indicated it was gtg. Oh well not my rifle, he will have to send it back.
FailureDrill-P099
04-22-12, 15:58
It has a 10 inch Troy MRF rail on it. Im going to have him bring it over and see whats up with the gas tube and base under the rail.
I had an M&P acting similar a couple of weeks ago. I found the lp gas block was loose and would move forward and backward. One of the screws was also missing. The barel was not dimpled for the screws.
I had to dimple the barrel and then loc-tite the screws for the gb. Once that was done, the gun was good to go.
I had an M&P acting similar a couple of weeks ago. I found the lp gas block was loose and would move forward and backward. One of the screws was also missing. The barel was not dimpled for the screws.
I had to dimple the barrel and then loc-tite the screws for the gb. Once that was done, the gun was good to go.
How old is the gun? I am pretty sure their GB's are all pinned on now.
C4
I then noticed the hammer pin was coming out and the hammer was not working properly.
That is typically a missing or defective J spring in the hammer. The J spring is supposed to engage the groove in the pin.
It has a 10 inch Troy MRF rail on it.
IF this was added after purchase then the warranty might be void. If not then...
Oh well not my rifle, he will have to send it back.
How old is the gun? I am pretty sure their GB's are all pinned on now.
C4
Yeah...I think they've been that way a while...my MP15T is about 3 yrs old and its pinned, as I understood it it was only the first year or so when they were not.
As to the OP, if this rifle isn't cycling the bolt carrier at all and never has done and everything else checks out, id strongly suspect there is some gasblock misalignment issue or the port is otherwise blocked / badly machined. From my own experience and reading listings on here by Grant etc, the last thing M@Ps do is not cycle....they are usually hugely overgassed - I run mine with a Springco extra power red spring and H2 buffer and it still always cycle the shittiest ammo that Tula can produce. Id have your buddy send the rifle in and get it sorted out.
FailureDrill-P099
04-23-12, 10:52
Thanks for the posts guys he will send it in. There are just to many things going on with his rifle.
Grant,
The one I had the problem with was an older one. Good to know they are pinning the gas block now.
FailureDrill-P099
04-27-12, 08:02
Updated the problem in the OP with pics.
looks like the gas block moving forward was the problem. Very wierd that the block and barrled were tapped for a pin but one was never put in the gas block. Just two small tention screws under the block.
So Smith forgot to pin the gas block?
So Smith forgot to pin the gas block?
Looks like it...obviously this rifle slipped through the cracks on a Friday afternoon....
I'd send that in and have them pin it.
Updated the problem in the OP with pics.
looks like the gas block moving forward was the problem. Very wierd that the block and barrled were tapped for a pin but one was never put in the gas block. Just two small tention screws under the block.
Those set screws will most likely never hold without the barrel being dimpled.
So I would call S&W CS and get a roll pin for it.
C4
FailureDrill-P099
04-27-12, 10:55
Those set screws will most likely never hold without the barrel being dimpled.
So I would call S&W CS and get a roll pin for it.
C4
Thats what I figured, good call on getting pin. Grant do you know if S&W uses streight pin or a taper pin with the low profile block?
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