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Discussion Starter · #1 ·
Cleaned the gas system prior to match. Gas piston is original 1988. Noticed rough edges at front and rear of piston. Should I replace piston? Any preference as a replacement. Old piston is grooved (six in front of hole and one in rear after the hole)
 

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Sadlak makes excellent pistons in polished stainless steel and TiN coated. They're also much cheaper than what I paid for my last new USGI piston...
 

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In the mean while I would get rid of those rough edges with a file and stone. Very carefully.
 

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New piston

Cleaned the gas system prior to match. Gas piston is original 1988. Noticed rough edges at front and rear of piston. Should I replace piston? Any preference as a replacement. Old piston is grooved (six in front of hole and one in rear after the hole)
Take the advise offer and stone off rough areas. A new piston, any piston, may reduce the accuracy of the rifle, the odds of it improving the accuracy are not in your favor after all the time you have had the piston in question, I assumed you fired many rounds . Art..
 

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So Art, Do you recommend replacing the entire gas system when you feel it may be going? I have been wondering about this myself.
 

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I think Art is alluding to the fact that the piston and the gas cylinder wear together. So if the piston has been in use with that gas cylinder for some time, and you go and change the piston only, your accuracy may go to pots because the piston is not matched to the gas cylinder. You'd want to replace both the cylinder and piston if you were to start part swappin'. I would not change the plug and lock at the same time unless there was something else that dictated that I needed to.

There were burs on the front edge of my gas piston on my (like new) 79,*** SAI rifle. I just carefully deburred with sandpaper I had present when I noticed. She shoots 2 MOA from field positions with Lithuanian M80, so I have seen no need to replace it.


SS
 

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Changing out Pistons Question

So Art, Do you recommend replacing the entire gas system when you feel it may be going? I have been wondering about this myself.
That is tough question, to my knowledge there is no hard evidence to support any position when it comes to pistons and gas cylinders. As to your question, it takes many rounds to wear out a Gas cylinder or a piston, particularly, if little rapid fire has been done.

The entire Piston to Gas Cylinder issue was never completed, the Service RifleTeams, they were investigating and working on this relationship when the Rifle of choice was change to the 5.56. so it was not competed. Gus Fisher has written on this subject, you may chase his Thread down and find a better answer.

I'll try to do a Thread on some of the experiences encountered regarding this Piston to Cyl. relationship soon. A generous amount time and testing was done, but in the end, we had no Formula for success. We did have improvement, a repeat of these tests would be very expensive today. There is a method to use that is practical to a point, I'll get around to that if you are interested. Art
 

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That is tough question, to my knowledge there is no hard evidence to support any position when it comes to pistons and gas cylinders.

There is a method to use that is practical to a point, I'll get around to that if you are interested. Art
I am interested...does that count ?DI2
 

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Art, I'm interested, too, if you have the opportunity. I've read Gus' writings on trying to find a direct correlation between gas piston size and accuracy, and am generally happy with my accuracy, but am always looking to learn more.
 

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I can't add more, it would be spectulatiom

Art, I'm interested, too, if you have the opportunity. I've read Gus' writings on trying to find a direct correlation between gas piston size and accuracy, and am generally happy with my accuracy, but am always looking to learn more.
Thank you, I am also interested also in Piston/Cly relationship. Without the support of more than I can expect, I think the subject will stay where it is.

The Stem of the Piston is just as interesting, maybe more because many more things can be done to it. I have not done them all but the several mods I've made have been impressive in accuracy, by impressive, I mean in terms of thousands of an inch in my rifles. There is a difficult taper that can be ground on the stem that eliminated piston stem bounce, this allow a free float through the D hole in other words.. I have also changed the combination of gas passages from the barrel to the piston, increasing Dwell time, this has added to my Goals, small amounts they might be, but at this point nothing else can be expected. One rifle has produce five shot groups under 1/2 inch and ten shots under one inch. I have to be realistic , this is a copy of a Service Rifle. Art
 

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Here is more to keep us confused. I've picked up two Tin coated pistons from different vendors. Today out of curiosity I measured them. The measurements were of the piston excluding the tail piece. They all measured different. The stock Springfield was in the middle, while one Tin coated was ten thousandths shorter. The other was ten thousandths longer. Last week I shot using the short one, the one thing noticeable was it kicked the brass to the right rear. I checked and the gas plug was loaded with carbon. Its been cleaned, and Monday I'm taking all three pistons with me to the range and see what results I get.
 

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Discussion Starter · #12 ·
Gas Piston #2

Well damn, who would have thought such a simple question would lead to such a complex answer. I am not a M1A mechanical wizard. I would have to send "Sweetlips" to SA to replace the gas system. Let me make sure I got this right. If I replace the old gas piston and gas plug with the new ones that arrived Friday I stand a chance of loosing the accuracy that this rifle has. I do not want that to happen as she shoots great. Double Damn. ARE YOU SURE!
 

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Me Myself keep several NOS gas pistons on hand Just in Case
 

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I installed a Sdalak TIN coated NM piston in my M1A NM,the orginal is still good looking,could this be a reason for my group size?they seemed to grow latley.Should I replace the gas cylinder and piston together when the piston wears out,and how many rnds.before I change? what should I look for with the piston to see when it needs changed.My M1A NM was made around the late 80's,it is all orginal USGI parts,not sure of the rnd.count I bought it used from a friend,and I've proably put 150rnds.through it myself,and I'm pretty sure that he has put less than a 1000rnds.through it before me.
 
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