Gas tube and piston mistake-Voila'

owlcreekok · April 10, 2006, 08:41

I did a real dumb thing yesterday. I took one of the R1's I am building to the range without verifying that the gas piston worked freely in the tube-MANUALLY.

First round, gas on "7". Bolt locked back, piston stuck, protruding about 2" into the action.

WTF ?

Me SO stupid.

I did it again.

Disassembled the thing to find the piston grinds to a halt, binding in the tube a short ways into it's range of travel. This IS the exact tube and piston that came with the R1 kit. I started packing up the R1 to give up when I found a gas piston in the rifle case that came out of my Stg kit. (replaced it with a US piston some months ago. "No Way" , I am thinking. Sure as snot, it fit the R1's tube and operates flawlessly.

I do not see any dents, or flaws in the tube, nor with the sticky piston. I haven't mic'ed the "bad" piston yet, but I will sometime.

NEVER NEVER NEVER fire a rifle without checking ALL moving parts by hand.

Stoopid Owl. (Lucky one too !)

**bykerhd** · April 10, 2006, 08:53

Try rolling that R1 piston on a flat surface. Watch the tail of it to see how much it bobs up & down. A little bend in the gas piston will often be the problem causing a bind up. Most of them have a little deviation(bend ?). As long as they function smoothly, you are ok.

Slow · April 10, 2006, 17:58

are you sure that piston wasn't the one we used saterday to hammer the trigger guard rivets in place ?????

ftierson · April 10, 2006, 18:39

Quote:

Originally posted by Slow
are you sure that piston wasn't the one we used saterday to hammer the trigger guard rivets in place ?????

...a comedian in every crowd...

Forrest

Vorpal_weapon · April 11, 2006, 13:00

+1 on Mr. bykerhd’s comments.

Yep, strange as it sounds, a slightly bent piston is a real drag (pun intended) and I have experienced several.

My first experience with one was on my Iz HB. A bent piston made the weapon barely operational with a fully closed gas system and it drove Curt and I crazy for a while. Now I roll test every piston before assembly - as described above by bykerhd – roll across a smooth desk top. If the head of that piston bobbles perceptibly on the roll test - I just replace it.

owlcreekok · April 11, 2006, 13:21

The range I frequent has just built some nice benches of good grade pressure treated lumber. Some 2 x 10's seemed nice and flat, so I rolled the suspect upon it. Even considering the dubious surface, the piston appeared straight. On a glass tabletop, it shows no wobble. Haven't chucked it in the lathe yet. The kicker on range day was when I inserted the piston into the gas tube backwards. About 2" or 3" into the trip it sticks. Turn the tube around and as soon as the piston gets to the polished area inside, it sticks.

I need to go out to the shop and mic the dang thing instead of feigning work and surfing the Files.

**bykerhd** · April 11, 2006, 15:20

Sounds like it's pretty straight all right.
If oversize, check what you are running in other FALs. You may be able to swap around with another one. I have one DSA gas piston I bought for one rifle that ended up in another because it was so far oversize. In fact out of several FALs I have, it only fits in this one. The funny thing is that the one it works in is a brand new Argentine barrel.

gunnut1 · April 11, 2006, 18:42

I know this is is a stupid question, but, you didn't over tighten the gas tube did ya? I is supposed to wobble. Remember, just tighten it down then back it off till the gas hole clears the port. But you know that! I would take the gas tube out, run the suspect piston thru it and chamfer the inside of the tube where the threads are just a bit. That sounds about the area it is hanging at. There may be a burr on it that is causing this piston to stick.

One other thing. I had a gas tube blow off of my G1. Have you checked the gas tube to make sure it is still attached? The short story is this. I was checking out my G1 build at Gibson's range. The gun cycled but the bolt didn't close all the way. Did what you did, pushed the piston back in and fired again. This time it closed. Shot again and the piston hung out again. 15 round later I figured I had better see what the problem was. Took the handguard off and the gas tube had blow off of the regulator.

Good luck!

Court in Fl · April 11, 2006, 19:56

After I install the gas tube I always do the test where you drop the piston in the tube without the spring and see if it falls in to the receiver.

I then install the spring and use a wood dowel to push the piston in the gas tube a few times to make sure it moves ok.

Good luck, Court in FL.

owlcreekok · April 11, 2006, 22:06

Quote:

After I install the gas tube I always do the test where you drop the piston in the tube without the spring and see if it falls in to the receiver.

THAT, good Sir, is what I did NOT do, for which kinds of things I earn the line.

"Me SO Stupid"

April 10, 2006, 08:41	#1
owlcreekok Registered FALaholic #: 15323 Join Date: Sep 2004 Location: Tejas Posts: 9,331	Gas tube and piston mistake-Voila' I did a real dumb thing yesterday. I took one of the R1's I am building to the range without verifying that the gas piston worked freely in the tube-MANUALLY. First round, gas on "7". Bolt locked back, piston stuck, protruding about 2" into the action. WTF ? Me SO stupid. I did it again. Disassembled the thing to find the piston grinds to a halt, binding in the tube a short ways into it's range of travel. This IS the exact tube and piston that came with the R1 kit. I started packing up the R1 to give up when I found a gas piston in the rifle case that came out of my Stg kit. (replaced it with a US piston some months ago. "No Way" , I am thinking. Sure as snot, it fit the R1's tube and operates flawlessly. I do not see any dents, or flaws in the tube, nor with the sticky piston. I haven't mic'ed the "bad" piston yet, but I will sometime. NEVER NEVER NEVER fire a rifle without checking ALL moving parts by hand. Stoopid Owl. (Lucky one too !) __________________ "It is necessary for the welfare of the nation that men's lives be based on the principles of the Bible. No man, educated or uneducated, can afford to be ignorant of the Bible." - Theodore Roosevelt - (1858-1919) 26th President of the United States FOUNDER- Free ggiilliiee Foundation hehe

April 11, 2006, 13:00	#5
Vorpal_weapon Registered FALaholic #: 17016 Join Date: Feb 2005 Location: scenic Oklahoma, USA Posts: 353	+1 on Mr. bykerhd’s comments. Yep, strange as it sounds, a slightly bent piston is a real drag (pun intended) and I have experienced several. My first experience with one was on my Iz HB. A bent piston made the weapon barely operational with a fully closed gas system and it drove Curt and I crazy for a while. Now I roll test every piston before assembly - as described above by bykerhd – roll across a smooth desk top. If the head of that piston bobbles perceptibly on the roll test - I just replace it. __________________ SI VIS PACEM PARABELLUM You knew the job was dangerous when you took it. NRA Life Member

April 11, 2006, 13:21	#6
owlcreekok Registered FALaholic #: 15323 Join Date: Sep 2004 Location: Tejas Posts: 9,331	The range I frequent has just built some nice benches of good grade pressure treated lumber. Some 2 x 10's seemed nice and flat, so I rolled the suspect upon it. Even considering the dubious surface, the piston appeared straight. On a glass tabletop, it shows no wobble. Haven't chucked it in the lathe yet. The kicker on range day was when I inserted the piston into the gas tube backwards. About 2" or 3" into the trip it sticks. Turn the tube around and as soon as the piston gets to the polished area inside, it sticks. I need to go out to the shop and mic the dang thing instead of feigning work and surfing the Files. __________________ "It is necessary for the welfare of the nation that men's lives be based on the principles of the Bible. No man, educated or uneducated, can afford to be ignorant of the Bible." - Theodore Roosevelt - (1858-1919) 26th President of the United States FOUNDER- Free ggiilliiee Foundation hehe

April 11, 2006, 18:42	#8
gunnut1 Moderator Gold Contributor FALaholic #: 1877 Join Date: Dec 2000 Location: The great Republic of Texas USA!!!!! Posts: 10,427	I know this is is a stupid question, but, you didn't over tighten the gas tube did ya? I is supposed to wobble. Remember, just tighten it down then back it off till the gas hole clears the port. But you know that! I would take the gas tube out, run the suspect piston thru it and chamfer the inside of the tube where the threads are just a bit. That sounds about the area it is hanging at. There may be a burr on it that is causing this piston to stick. One other thing. I had a gas tube blow off of my G1. Have you checked the gas tube to make sure it is still attached? The short story is this. I was checking out my G1 build at Gibson's range. The gun cycled but the bolt didn't close all the way. Did what you did, pushed the piston back in and fired again. This time it closed. Shot again and the piston hung out again. 15 round later I figured I had better see what the problem was. Took the handguard off and the gas tube had blow off of the regulator. Good luck! __________________ Texas, it's a state of mind!!!! The human race is not the pinnacle of evolution. We are but one evolutionary out come.

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April 10, 2006, 08:53	#2
bykerhd Dinosaur Bronze Contributor FALaholic #: 2798 Join Date: Mar 2001 Location: Burlington Vermont area Posts: 13,262	Try rolling that R1 piston on a flat surface. Watch the tail of it to see how much it bobs up & down. A little bend in the gas piston will often be the problem causing a bind up. Most of them have a little deviation(bend ?). As long as they function smoothly, you are ok.

April 10, 2006, 17:58	#3
Slow Registered Bronze Contributor FALaholic #: 17330 Join Date: Apr 2005 Location: Houston, TX Posts: 1,653	are you sure that piston wasn't the one we used saterday to hammer the trigger guard rivets in place ?????

April 11, 2006, 15:20	#7
bykerhd Dinosaur Bronze Contributor FALaholic #: 2798 Join Date: Mar 2001 Location: Burlington Vermont area Posts: 13,262	Sounds like it's pretty straight all right. If oversize, check what you are running in other FALs. You may be able to swap around with another one. I have one DSA gas piston I bought for one rifle that ended up in another because it was so far oversize. In fact out of several FALs I have, it only fits in this one. The funny thing is that the one it works in is a brand new Argentine barrel.

April 11, 2006, 19:56	#9
Court in Fl Curio & Relic FALaholic #: 5046 Join Date: Dec 2001 Location: South Florida Posts: 3,150	After I install the gas tube I always do the test where you drop the piston in the tube without the spring and see if it falls in to the receiver. I then install the spring and use a wood dowel to push the piston in the gas tube a few times to make sure it moves ok. Good luck, Court in FL.