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Posted: 10/4/2012 6:03:17 PM EDT
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Took my Poly M14S today and it was a straight pull bolt gun. Most of the time, the bolt didn't even move at all. Once, it opened enough to extract the casing but closed on it causing a long-ways stovepipe.
- Made sure it wasn't on grenade launcher setting. - Tried Silver Bear .308 (worked in my last Poly M14S) and FGMM 7.62x51. I took it home to diagnose it some more. - Piston has a suction cup effect when the gas plug is on. Piston falls due to gravity but slowly. - Piston moves freely with the gas plug removed. Falls at a natural rate with gravity. - All gas ports are clear. - Cleaned gas chamber and piston with solvent. Did not lube. After cleaning, there was still the suction cup effect on the piston. What am I doing wrong or what is wrong with my rifle and how do I fix it? |
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Hmmmmmmmm....
Well, I suppose the piston / gas system could be gummed up. You said it moves though. You could try and spray some gun scrubber or brake cleaner in and around it to clean it out. Other than that, you have to go back to the basics. Is it lubed properly? I forget can one do a tip test on an M1A/M14? Or meaning is the op rod or bolt or anything rubbing on something or getting caught somewhere. I wonder if your mag is too far up that it's jamming on the bolt. Aren't you the one saying it wont seat? No wait, that was someone else. What kind of mag do you have? Does it hand cycle without too much effort? It takes a little bit of effort to cock the hammer, but it shouldn't be real hard to do. Is there any rub marks on the inside of the stock, where the op rod might touch? That's all I can think of for now. |
| Is the gas port in the barrel aligned with the gas port in the gas cylinder? The 7/64" hole in the bottom of the gas cylinder should go directly into the barrel. With the valve open, slide a nail/pin/dowel into the hole and verify if the gas cylinder and barrel holes are aligned. If not, you would get the problem you have. |
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Here's something to read to let you understand how it works... Don't know if it will help though...
http://www.americanrifleman.org/articles/m-14-gas-cylinder/ |
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should be a slight suction with the plug installed.
Things to try> 1. ensure the gas system in lined up properly. (easy way is to get a 1/16 allen and slide it into the gas bleed off port of the cylinder, wiggle it a bit, until it passes through the other 2 holes, look into muzzle and see if you can see th wrench) if not shim it till you can. 2. make sure the rifle does not have op rod drag, especially if you have changed stocks. (op rod dragging against side of the stock) 3. make sure the rifle is lubed to spec with quality grease, (if it moves grease it if it rotates oil it) I also like putting a light coat of grease on the bottom of the barrel hump where the op rod rides 4. make sure the spindle valve is actually open or closed. (again allen wrench is the easiest) hope this helps |
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Quoted:
Did not verify if gas ports line up yet. Even with the gas cylinder off, there's the suction cup effect where the piston has a hard time moving. Will align gas ports and try a coworker's piston in my rifle next week. Bolt hand cycles like normal. OK, maybe I'm crazy, but when I read "Even with the gas cylinder off, theres' the suction cup effect where the piston has a hard time moving." my brain goes, well of course, that's because when it's turned off, it closes the hole. What happens when you turn it on? Because that allows the hole or gas system to be open, to allow the gas from the barrel to blow by through the port, or hole, and cycle the piston, thus cycling the action. If it's closed, it's just that, closed. And the port is "cut off", not allowing gas to blow by. Therefore, there probably would be a suction affect. And I would think less so, with it open. I forget how mine is, but I've never had a problem with function and I don't think it dangles around all loosy goosey. But I can verify that in a bit. |
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Quoted:
Quoted:
Did not verify if gas ports line up yet. Even with the gas cylinder off, there's the suction cup effect where the piston has a hard time moving. Will align gas ports and try a coworker's piston in my rifle next week. Bolt hand cycles like normal. OK, maybe I'm crazy, but when I read "Even with the gas cylinder off, theres' the suction cup effect where the piston has a hard time moving." my brain goes, well of course, that's because when it's turned off, it closes the hole. What happens when you turn it on? Because that allows the hole or gas system to be open, to allow the gas from the barrel to blow by through the port, or hole, and cycle the piston, thus cycling the action. If it's closed, it's just that, closed. And the port is "cut off", not allowing gas to blow by. Therefore, there probably would be a suction affect. And I would think less so, with it open. I forget how mine is, but I've never had a problem with function and I don't think it dangles around all loosy goosey. But I can verify that in a bit. I meant off as in removed from the barrel. Sorry for the lack of clarity. |
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Quoted:
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Quoted:
Did not verify if gas ports line up yet. Even with the gas cylinder off, there's the suction cup effect where the piston has a hard time moving. Will align gas ports and try a coworker's piston in my rifle next week. Bolt hand cycles like normal. OK, maybe I'm crazy, but when I read "Even with the gas cylinder off, theres' the suction cup effect where the piston has a hard time moving." my brain goes, well of course, that's because when it's turned off, it closes the hole. What happens when you turn it on? Because that allows the hole or gas system to be open, to allow the gas from the barrel to blow by through the port, or hole, and cycle the piston, thus cycling the action. If it's closed, it's just that, closed. And the port is "cut off", not allowing gas to blow by. Therefore, there probably would be a suction affect. And I would think less so, with it open. I forget how mine is, but I've never had a problem with function and I don't think it dangles around all loosy goosey. But I can verify that in a bit. I meant off as in removed from the barrel. Sorry for the lack of clarity. I thought that was a possibility. So you have it off and the gas port open and it's kind of sticky, eh? |
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Did not verify if gas ports line up yet. Even with the gas cylinder off, there's the suction cup effect where the piston has a hard time moving. Will align gas ports and try a coworker's piston in my rifle next week. Bolt hand cycles like normal. OK, maybe I'm crazy, but when I read "Even with the gas cylinder off, theres' the suction cup effect where the piston has a hard time moving." my brain goes, well of course, that's because when it's turned off, it closes the hole. What happens when you turn it on? Because that allows the hole or gas system to be open, to allow the gas from the barrel to blow by through the port, or hole, and cycle the piston, thus cycling the action. If it's closed, it's just that, closed. And the port is "cut off", not allowing gas to blow by. Therefore, there probably would be a suction affect. And I would think less so, with it open. I forget how mine is, but I've never had a problem with function and I don't think it dangles around all loosy goosey. But I can verify that in a bit. I meant off as in removed from the barrel. Sorry for the lack of clarity. I thought that was a possibility. So you have it off and the gas port open and it's kind of sticky, eh? It's only sticky with the gas plug installed. |
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There's a suctiony feel as long as the gas plug is installed. It doesn't matter if the valve is open or closed or if the gas cylinder is on or off the rifle. That how it should feel... Did you like at what I posted? The hole in the piston should line up with the gas port on the barrel...when the piston moves it "closes" the gas port 
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Clean with Drills
Any binding of the op rod during its cycle. The piston should move with the rifle titled at 45 deg and the bolt locked to the rear. |
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I'm wondering if he's not getting some kind of binding from the op rod itself. What kind of stock do you have it in, and was it the one that came with the rifle? If you take your recoil spring out, and assemble it without it, will the op rod and bolt move freely when you tip the rifle up and down. Meaning close the bolt, and tip the butt end down. Will it open freely or does it seem like it's rubbing somewhere? And vice versa. Does it close or go forward if you tip the muzzle down. We do this with Garands moreso, but I suppose it could show you if it's getting hung up somewhere. Or maybe your op rod is bent. ?????
It's weird how it stayed closed most of the time, but then opened once. You'll like it once it works, just hang in there. I'm sure there is a reasonable explanation. I don't remember if you said you lubed it or not. With some grease. |
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Quoted:
Took my Poly M14S today and it was a straight pull bolt gun. Most of the time, the bolt didn't even move at all. Once, it opened enough to extract the casing but closed on it causing a long-ways stovepipe. - Made sure it wasn't on grenade launcher setting. - Tried Silver Bear .308 (worked in my last Poly M14S) and FGMM 7.62x51. I took it home to diagnose it some more. - Piston has a suction cup effect when the gas plug is on. Piston falls due to gravity but slowly. - Piston moves freely with the gas plug removed. Falls at a natural rate with gravity. - All gas ports are clear. - Cleaned gas chamber and piston with solvent. Did not lube. After cleaning, there was still the suction cup effect on the piston. What am I doing wrong or what is wrong with my rifle and how do I fix it? One thing most guys over look is the gas cylinder plug. Carbon build up inside the plug (the hole inside) will decrease the amount of gas pressure required to cycle the bolt & op-rod. USGI gas plugs can be cleaned out with a "P" drill bit. I don't remember the hole size on the Poly's but it can be cleaned the same way. Also, the inside of the piston should be cleaned every so often to prevent the same problem. USMC armorers put 1-2 drops of Hoppes #9 in the gas cylinder (thru the bottom hole) after everything is installed to prevent carbon build up & make cleaning easier. It works well. The gas piston moving slowly as you described is normal. If it just drop down quick with the plug installed, you would have a worn cylinder or piston which is not good. . |
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