Does your problem happen with each mag or only one or two of them?
Every mag
So probably not a mag issue. Like folks said scrub your chamber well; grease bolt/op rod and fire using Win or Fed 7.62x51 m80 ball ammo (if you have any to spare). Still malfunctioning send back to Sprfld Armory! Sorry best I can do long distance. Good luck, remember M1a is still one of the best battle rifles ever.
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I appreciate your input. Thank you very much
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I started writing this last night but got called away, I shot M1Aās and M14ās on the Navy Rifle Team from 1988 to 1994. M1Aās are pretty durable as far as they go so an āall of the sudden problemā is usually an ammo issue but yours sounds like a multi phase issue with the gas system.
I A$$uME that you know a bit about the rifle and would notice if the bolt has jumped the Op Rod so that it isnāt where it is supposed to be.
A$$uMEing that the gun is assembled correctlyā¦ there is no way to get to the gas hole that is drilled into the barrel and there is no way without pulling the gas system off to inspect the hole or the gas piston housing. That being said there are things you can do. Step one pull the Op Rod back and lock it to the rear. Tip the gun forward and aft and listen to see if you can hear the gas piston sliding back and forth. You SHOULD be able to hear it slide back and forth. Take the rifle out of the stock and put it and the trigger group someplace safe. Take the OP Rod, spring and guide out and put them with the stock.
(This is a match thing but it works for GP too. Use some finger nail polish or a paint pen and paint the joint between the gas plug and the gas piston lock ring at 3:00 and 7:00. Paint the gas piston lock and the gas piston housing at 5:00 and 9:00. Works good for putting things back together)
Take a correctly sized wrench to the gas plug and unscrew it, point the gun down. If the piston doesnāt fall out you have soot/gunk/fouling and crap issues. If the gas plug wonāt come out by a MINOR application of wrench you will need a āFigure 8ā wrench (you can use a Ford wrench or (GULP) channel locks) to hold the gas block still while you break loose the gas plug. DONāT SCREW THIS UP. If you canāt hold the rifle by the gas block in one hand and smack the disassembly wrench or 6" 1/4" drive socket wrench and break the plug loose you NEED a figure 8 wrench to hold the gas block still or you will twist it off the cross pin and it gets ugly from there.
Once you get the gas piston out you will need to clean the carbon out of the gas piston and the housing. Use a size āPā drill bit and a #15 drill bit to do this, which goes where is obvious. Do it by hand slowly trying to keep it straight. You are scraping out carbon not reaming the holes. DO NOT ADD OIL/CLEANER OR SOLVENT AT THISA TIME. They make a tool for this and it looks just like a screw driver handle with a drill bit sticking out of either end, probably at the same place you can find a Figure 8 wrench.
Now plug your chamber with whatever will not get eaten by whatever carbon/copper cleaner you are about to fill your bore with. Turn the rifle muzzle straight up and put it someplace that it wonāt get knocked over and wonāt mind the smell of the solvent for 24 hours + (hint: if your garage is not detached itās not a good choice, neither is anyplace INSIDE your house) . Fill your bore all the way to the muzzle with said solvent and STOP! It will leak into your gas system and fill that up too. No need to add more. Let it sit for 24 hours then dump it someplace that doesnāt mind the stink. Clean the bore with a bore brush and muzzle guide (you have one of those right? They have them with the wrench and drill bits place). Squirt pressurized brake cleaner or similar into the hole waaaay at the back of the gas piston housing. Itās going to end up in your bore (they are connected). Go back to the top of this paragraph and start over until you read this again.
While you are waiting for the bore and gas system to soak, clean your trigger assembly as best as you can. Hose it down with brake cleaner and get it DRY, blow it off with compressed air. A drop of oil on the trigger assembly cross pin is almost too much. a q-tip dipped in oil and then dabbed on a paper towel is enough to oil the contact surfaces of the hammer, sear and other rubby bits. Clean your stock with a dry paint brush and compressed air. If itās really dirty use brake cleaner and a rag. Oil the metal bits for protective purposes by wiping them with an oily rag. Add a āLITTLEā dab of grease on the bottom of the metal ferrul at the pointy end of the stock. This is where the front of the rifle contacts the front of the stock. Clean and light oil the spring and spring guide.
Once you have done all the above clean the bore with more solvent and your bore brush. Then lay in the brake cleaner from the bore and the gas housing side and blow it all dry. Run ONE lightly oiled patch down the tube and then FIVE dry patches. Mop your chamber with whatever chamber cleaning mop you prefer then put ONE more dry patch down the tube. You should end up with a bore and gas system that is as close to factory new as you can reasonably get.
Reassemble in reverse order and go shoot the gun. Evaluate for operation and function. Do NOT clean the bore or the gas system EVER until the rifle starts to slow down or has other issues. You will probably only have to do this 4 -5 times in the life of your barrel unless you are running really dirty/corrosive ammo.
Yes I just said clean your rifle bore 4 - 5 times in its LIFETIME. Obviously if you take it swimming or something you might want to clean it, other than that LEAVE IT ALONE. Clean the chamber and if you MUST drag a DRY bore snake from the chamber end out the muzzle. Donāt put anything in the bore that is not boolit or fire unless you have to.
Cheers,
Craig6
I forgot, disassemble and clean the bolt too, just enough oil to keep it from rusting. A little grease in the op rod notch and on the roller bearing of the bolt is a good thing too.
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Seems you know a great deal about the M1A. I appreciate all the detailed info. Seems I have my work cut out for me.
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@Peter102 M1Aās and M14ās are REALLY easy to work with. Hooking optics up to them is a different story. Dirty ammo will foul the gas port, lacquered cases are fine unless they get hot and then your chamber is the issue. I know one civilian smith with a rep for M1Aās that has chamber reamers on the long rod custom under cut 0.002", 0.004" and 0.006" less than normal spec to address the issue of lacquer in chambers. He says it cuts his cleaning down by 75%, once he breaks through the surface of the lacquer, solvents do their thing much better. I was amazed at how much and many curls of fried lacquer came out of a chamber when he demonstrated.
Do you have to do all the above to get your stick back up and running? No. If the gas system is clogged unclog it. The lesser of two evils is to fill the gas piston housing up with solvent and lean it back til it runs into the bore and let science do itās thing. Skin the cat anyway you can.
There is always the chance that none of the above will work in which case I hope you say so.
Cheers,
Craig6
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Thanks Craig. 
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I acctually had a very easy time with my optics. I got a surefire reflex sight and it fit perfectly. By some miracle, I didnāt have to zero it, it just have to be perfect from the company. Luck. I hate zeroing. It can be tedious. I bought a replacement upper hand guard that was all metal and has a piccatiny rail running along the top from the barrel to the chamber. So I fit both my sight and flashlight/laser on it.
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this is the gas block wrench
and the drills
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Thank you @Craig6 for your experience and knowledge with rifles and I look forward to reading your posts brother.
IIRC there is a thing that may be needed when you reassemble the M1Aā¦
has to do with the front portion where the barrel and stock come togetherā¦
the metal piece which is rather thin and springy that is kinda lose on the barrel needs to be pulled back toward where it will mate up with the stockā¦ IIRC when they are mated there should be about 24 lbs of pressure there???
when I was in the military and we went for quals (boot camp) at the ranger we were told to NOT disassemble the rifleā¦
thought that was oddā¦ but once I saw the diagram and the amount of pressure on that connectionā¦
it all made senseā¦ also notice a tool that looked odd when I picked up a rifle for qualsā¦ later onā¦
had a rather long handle and a u shaped section on the endā¦ hard to explain but the u shaped piece had two odd prongs that bent back onto the uā¦ figure that was for pulling the piece on the M14 back???
item 22 ( kinda hard to see)
this is a btter picture of the part Iām referring to
you should have a good solid fit there with the stock when reassembled no slop!
supposedly that reduces your shots going all over and often results in very tight groups???
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Thinking the springy piece was a shim? I shim my gas block to remove that slop, and torque to 18"/lbs.
Editā¦just looked up #22 on my m14 Tek matā¦barrel band, and shims go in that areaā¦ Dang, you got me diggingā¦ready to pull my Scout out and take a pic, but itās happily snuggled up in itās sock right now 
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a link for some of the armorers toolsā¦
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donāt think that is the meaningā¦ if the fit between the stock and that springy piece is sloppyā¦
reports are your shots will tend to string on you???
whereas IF you pull/bend slightly??? that springy piece so it mates with the stock WELLā¦
it will reduce shot spreadā¦ for some considerably???
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So I would like to thank everyone for their advice and input. I decided to take my rifle into a shop for a full cleaning and inspection. Sixty dollars later, the culprit of my troubles was a faulty/ loose gas cylinder plug. Bought a new one and all is good.
Many thanks to everyone again!
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Good to hear the problem is solved.
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Glad you got it sorted, my experience is the opposite of loose but I guess it could happen.
Cheers,
Craig6
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