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Discussion Starter #1
Since moving my SOCOM into a Troy MCS, the weapon is having failure to feed issues. Manually cycling the action always feeds. The problem occurs after firing... proper ejection then a closed bolt on an empty chamber. Once again, manually cycling the weapon will load a new round. Mags are unquestionably good (worked flawlessly previously; quality US-made).

Full info: the weapon is a stock SOCOM 16 with the exception of the op rod and piston (Sadlak), a new op rod guide spring, and a USGI extractor. All of this worked in the SAI fiberglass stock. Two changes have been made since the problem began: put SOCOM in MCS, replaced stock muzzle brake with this one from NoKick.

At first I thought it was the way the trigger group was holding the mag in place (there are allen-screw adjustments), but after working with adjusting it, I'm no longer certain that's the case.

Is it possible that the weapon is somehow "short cycling"... just enough to eject but not far back enough to catch the next round?

I'd love to fix this myself, but I'm open to sending it to Fulton or elsewhere to have it done right (I'm no gunsmith). All I care about is that my MBR goes "bang" every time I pull the trigger MCORPS1. An unreliable weapon is 100% useless to me.

Any help is appreciated, fellas.
 

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the weapon is a stock SOCOM 16 with the exception of the op rod and piston (Sadlak), a new op rod guide spring, and a USGI extractor
I bet your problem has something to do with the piston or spring. I read something about NM pistons not working like the standard pistons. SRM

EDIT- Here it is from SADLAK:

IMPORTANT: THE NATIONAL MATCH GROOVE IS INTENDED FOR NM GRADE AMMO ONLY AND IS NOT RECOMMENDED FOR SURPLUS BALL AMMO OR OTHER LOWER POWER AMMO.
If you plan to shoot NM ammo then the groove in the piston is useful. Otherwise, it was not intended for regular ball ammo (not enough power). The groove provides a more consistent pressure against the op rod by bleeding off some of the excess pressure inherent in high-power Match ammo. This results in a slight recoil reduction to help "get back on target" during rapids. It also breaks the vacuum between the piston and the cylinder allowing the shooter to hear the piston slide down to confirm it isn't fouled.
 

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Discussion Starter #3
Thanks, SunRiverMan, but I'm already using the standard Sadlak TiN piston, not the NM (grooved) one.

All of the parts I listed (and the magazines) were working properly in the SOCOM for years before I put the weapon in the Troy MCS and added the new muzzle brake. That's why I'm thinking it has to do with the new chassis installation or brake.
 

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The first thing I would do is to try the tilt test in the TROY. I don't have one so I don't know if it's possible. If it is, I would start there. Next, I would ask if this is the first time you have removed the gas system since you owned it. Remove your gas plug and piston and check that a 1/16" allen wrench will insert into the vent hole in the gas cylinder and into your barrel.
 

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Cycle

+ 100 Tony, definately sounds like a op rod scenario or op rod spring binding up, if the gas is good to go. Has to be rubbing somewhere or over torqued on the chassis somewhere. Nothing serious I think, if you take it back down you will more than likely see where it's hitting or rubbing.
 

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Discussion Starter #6
troyben:
Thanks for the tips. The tilt test went fine. Action moves freely. The piston also moves freely of its own weight, but doesn't just flop back-and-forth. That is, it is affected by the air going into and out of the cylinder, but I assume that's normal.

As for your other question, I've had the weapon for a while and am a conscientious cleaner. I've got all the Sadlak tools for keeping the piston & plug clear, etc., etc. Everything there looks good.

Cylinder vent hole is properly aligned (I found a great little tool somewhere at a gun show that measures that).

ripsaw:
Thanks to you too. Regarding the "over torqued" possibility, but I'm not sure where to look on that. The MCS is a pretty solid bolt-on frame, and I don't see anywhere where it could or would be interfering with the action. Can you be more specific?

One question I do have regarding torque is what is appropriate for the gas plug. Do you know what the rule is?

Now...

I'm concerned again about the trigger group. When first set into the stock after adjusting the allen screws, the guard moves freely back to within about 1/8" from the trigger (per Troy instructions). Then, it takes a good amount of pressure to lock it in place. It then seems locked in solid and cycles fine manually. Now the odd part...

When I go to remove the group, I pull on the back of the trigger guard, but instead of the guard simply unlocking, it unlocks AND the whole group comes out. Almost like it's not in there properly in the first place. It would do this sometimes in the original SOCOM stock, but I never had any issues with performance so I never looked into it any further.

Is this trigger group thing a red herring, or could there be something to this?

Anyhoo, that's the state of it at this point. Thanks so much for the ideas so far. What else ya got? This is driving me nuts. ALCOHOLIC1
 

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Gas plug torque is 120 inch pounds to 23 foot pounds

http://m14tfl.com/upload/showthread.php?t=76707

I'm curious; have you function tested the rifle? Cycle the action, pull the trigger and hold it. Cycle the action and feel for binding. Release the trigger and pull again to ensure proper hammer fucntion. See if this test feels different in the original stock.

Also see if your trigger guard is bent. It seems like some excessive force is being used and the trigger group is not fully locking in place on the receiver legs.
 

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Can't believe I missed this....

Try swapping in your original spring guide or comparing how it feels with the Sadlak. Some SAI's don't like NM spring guides.
 

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Trigger group

In relation to torque I was referring to the tightness of the trigger group, perhaps the wrong word. I meant that when it doesn't fit properly it takes a lot of pressure, thats the word, to lock it in, and maybe it was putting the whole thing in a bind somewhere. By coming out like you described without rotatating the trigger guard on up, it sounds like something is amiss. Do you have a camera to post a pic of the bottom with the action sitting in it, Minus the trigger group? Tony might be on to something going back to what was in there previous. The piston and guide back to before, in the new stock, and see what happens, at least it could narrow the search, but the trigger group still doesn't sound like it is locking in properly.
 

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Thughes,
I had a very similar problem to yours when I recently installed a Troy on my Scout. My problem was that the gas lock was not tight enough and gas was leaking out, preventing a full cycling of the bolt. I flipped the gas lock, tightened much more than it had been when it was in the factory stock and the problem was solved. I know what you mean by the allen screws under the trigger group. I fiddled with them for a while and finally settled with them just barely above flush with the bottom of the reciever.

Good luck,
JoeCIB3RANGRJW
 

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Well since everything else worked in the SAI stock then I would do a tilt test. If it passes the tilt test, I would put it back into the original stock. If it still fails to work, I would swap back the stock gas lock/brake system.
 

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Discussion Starter #13
What ammo are you using? I have seen SOCOM's short stroke on weak (read cheap) ammo.
Various. When I discovered the problem I was using Lithuanian surplus. This time it was a box of Argentinian I grabbed and took to the range. This is all quality surplus stuff that functioned fine before the stock & brake switch.
 

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Discussion Starter #14
I had a very similar problem to yours when I recently installed a Troy on my Scout. My problem was that the gas lock was not tight enough and gas was leaking out, preventing a full cycling of the bolt. I flipped the gas lock, tightened much more than it had been when it was in the factory stock and the problem was solved.
I'm going with a hunch... I think I'm having a similar problem. I'm going to put the stock brake (built into the gas cylinder lock) back on, and properly torque the lock. Now I just need the time to do that and get out to the range...

Thanks everyone for the input so far USA2
 

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Discussion Starter #15
OK. Still no dice.

I put the original gaslock/brake back on (they are one piece on the SOCOM) and tightened the plug to spec.

First 20 rounds went without a hitch. Reloaded the same mag and ran into both failure to feed and also now jamming (round going partly into the chamber, bolt closing half-way on top of it).

I noticed in another thread that gaslocks should not easily hand tighten to 6-o'clock. Mine will hand tighten to 8:30, so 6 is actually a little loose for me. I can't imagine using my wrench to crank that thing around 280 degrees is the correct solution... is it? Should I try shimming? What about having a gunsmith sand the lock down to allow for a proper fit w/o extra parts?

What should I try next? I'm at wits end here. Thanks all...
 

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Discussion Starter #16
Found it!

With all the rounds I've been putting through the rifle trying to find the problem, the problem finally showed its ugly head... the op-rod is rubbing against the frame of the SOPMOD stock.

Anyone else with a SOPMOD run into this issue?

So, based on the photos below, what is recommended? Obviously, I'm going to remove the spur that's forming, but what else? Dremel the stock for greater op-rod "slop"? (The SOCOM op-rod has quite a bit of up/down movement to it).



 

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Discussion Starter #18
Here we go again

The wear I discovered may be due to bolt/hammer friction.

I said I passed the tilt test. Here's what happened...
  • action out of stock - pass
  • action in stock - pass
  • action in stock w/ trigger group - stops on contact w/ hammer
On a Garand, I think the action is supposed to stop on the hammer, so I thought I was good. Other posts here, however, indicate that travel should continue (presuming cocked & safety engaged).

So, should my action stop at the bolt or not? If not, what are my next steps?
 

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I have one rifle that passes over the hammer without contact and one that doesn't. In the tilt test thread, we talked about it a few posts down and determined that it is not indicative of a problem. If it's hanging up on the hammer, it's okay.
 

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check the op rod guide for wear inside
don't know much on the type of stock but you shouldn't have excessive up/down play in op rod
front stock mount may need adjustment
 
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