Tight Piston?

rotty · August 13, 2005, 20:09

I have been trying to trouble shoot my carbine build, last two times i tried it i had a case stuck in the chamber, gun was acting as only a single shot.
Imbel kit, imbel reciever, bbl cut to 18.75" and gas port opened up to .119.

Still acting up, well anyway, tonight i discovered that the iston is pretty snug in the tube....
It is a tapco piston and a new tube.....Is there a smaller psiton i could try, anyone have one?
I beleive the timing is good, I had the bbl installed by Ken at globel trades.

Any ideas? piston? tube?

Thanks

Pistolwiz · August 13, 2005, 20:16

Do a drop test on the piston. Take out the bolt and carrier. Then pull the piston and spring. Drop the piston inside the tube and see where it stops. Chances are that the tube has a ding in it. Or that the pin was instaled without being lined up on one of the flats on the tube threads.

rotty · August 13, 2005, 22:31

It stops almost even with teh gas port opening, not a hard stop either, it just slows down there. But it will go past, its just snug, I know i didnt put the tube in so the flats were down....or put the pin in wrong....
It is a new tube, and hasnt been bent or anything...with my calipers the head measures about .431...
It just seems to be a snug fit.

**bykerhd** · August 13, 2005, 22:56

Roll the piston on a hard , flat surface and check for wobble. The piston may have a slight bend in it. Longest lasting and best fix is to replace the gas piston if that is the case. I've had two bent as received from different vendors so far. One was definitely new and the other was supposed to have been.

Court in Fl · August 13, 2005, 23:05

Put the piston in the gas tube backwords and see where it hangs up.
If the head moves freely it may be draging at the gas cylinder end.

I had more than 1 gun that needed the hole in the gas cylinder opened up a little bit.

Try cleaning out the gas tube with a .50 brush.

Most of the pistons I have seen are about .429 to .430.

Good luck, Court in FL.

rotty · August 13, 2005, 23:33

Rolled piston, seems fine...
dropped in backwards, once the head gets pas the gas block area, it drops right down freely, once its past the gas block area, seems to be snugest there.
I'll get a differnt gas piston and see what happens.

**Hebrew Battle Rifle** · August 14, 2005, 01:26

Hey rotty:

Sometimes the mouth of the gas tube will get squeezed. If so, it will cause the drag that you are describing.

Aifwikir · August 14, 2005, 14:16

If you install the gas tube and tighten it down this will press the split end together. The gas tube should be turned in until it starts to get snug, then backed out to line up the cross pin. The gas tube should wobble just a little. If you have tightened it down and compressed the split end, you should remove it and open it up again. Just take a large flat tip screw driver and press it into the split on both sides of the tube. Your gas piston is the right size. Before you buy anything else try this out. You don't have to use the "Magilla Gorilla" method of tightening on it, just light pressure and when re-installing the gas tube, use thumb and index finger pressure only.

Hope this works out for you.

Aif

August 13, 2005, 20:09	#1
rotty Registered FALaholic #: 2110 Join Date: Jan 2001 Location: Montague, MI USA Posts: 884	Tight Piston? I have been trying to trouble shoot my carbine build, last two times i tried it i had a case stuck in the chamber, gun was acting as only a single shot. Imbel kit, imbel reciever, bbl cut to 18.75" and gas port opened up to .119. Still acting up, well anyway, tonight i discovered that the iston is pretty snug in the tube.... It is a tapco piston and a new tube.....Is there a smaller psiton i could try, anyone have one? I beleive the timing is good, I had the bbl installed by Ken at globel trades. Any ideas? piston? tube? Thanks __________________ Good... Bad.... I'm the guy with the gun!

August 13, 2005, 20:16	#2
Pistolwiz Registered FALaholic #: 4378 Join Date: Oct 2001 Location: WA Posts: 5,343	Do a drop test on the piston. Take out the bolt and carrier. Then pull the piston and spring. Drop the piston inside the tube and see where it stops. Chances are that the tube has a ding in it. Or that the pin was instaled without being lined up on one of the flats on the tube threads. __________________ "The constitution is not a bunch of suggestions. It's the law." "People will chew and swallow an entire sweet and delicious brick of lies. And enjoy it. Rather than taste one bitter grain of truth. No wonder they are hoodwinked so easily." "I don't run with lemmings...even well armed ones." "If we had as many misconceptions about the FN FAL as we do about the constitution. The body count from accidents would be much, much higher around here."

August 13, 2005, 22:31	#3
rotty Registered FALaholic #: 2110 Join Date: Jan 2001 Location: Montague, MI USA Posts: 884	It stops almost even with teh gas port opening, not a hard stop either, it just slows down there. But it will go past, its just snug, I know i didnt put the tube in so the flats were down....or put the pin in wrong.... It is a new tube, and hasnt been bent or anything...with my calipers the head measures about .431... It just seems to be a snug fit. __________________ Good... Bad.... I'm the guy with the gun!

August 13, 2005, 23:33	#6
rotty Registered FALaholic #: 2110 Join Date: Jan 2001 Location: Montague, MI USA Posts: 884	Rolled piston, seems fine... dropped in backwards, once the head gets pas the gas block area, it drops right down freely, once its past the gas block area, seems to be snugest there. I'll get a differnt gas piston and see what happens. __________________ Good... Bad.... I'm the guy with the gun!

August 14, 2005, 01:26	#7
Hebrew Battle Rifle Horses Ass Bronze Contributor FALaholic #: 5777 Join Date: Mar 2002 Location: Arkansas Posts: 6,812	Hey rotty: Sometimes the mouth of the gas tube will get squeezed. If so, it will cause the drag that you are describing. __________________ THANK YOU JESUS

August 13, 2005, 22:56	#4
bykerhd Dinosaur Bronze Contributor FALaholic #: 2798 Join Date: Mar 2001 Location: Burlington Vermont area Posts: 13,262	Roll the piston on a hard , flat surface and check for wobble. The piston may have a slight bend in it. Longest lasting and best fix is to replace the gas piston if that is the case. I've had two bent as received from different vendors so far. One was definitely new and the other was supposed to have been.

August 13, 2005, 23:05	#5
Court in Fl Curio & Relic FALaholic #: 5046 Join Date: Dec 2001 Location: South Florida Posts: 3,150	Put the piston in the gas tube backwords and see where it hangs up. If the head moves freely it may be draging at the gas cylinder end. I had more than 1 gun that needed the hole in the gas cylinder opened up a little bit. Try cleaning out the gas tube with a .50 brush. Most of the pistons I have seen are about .429 to .430. Good luck, Court in FL.

August 14, 2005, 14:16	#8
Aifwikir Registered FALaholic #: 2187 Join Date: Jan 2001 Location: Magazine, Arkansas Posts: 3,061	If you install the gas tube and tighten it down this will press the split end together. The gas tube should be turned in until it starts to get snug, then backed out to line up the cross pin. The gas tube should wobble just a little. If you have tightened it down and compressed the split end, you should remove it and open it up again. Just take a large flat tip screw driver and press it into the split on both sides of the tube. Your gas piston is the right size. Before you buy anything else try this out. You don't have to use the "Magilla Gorilla" method of tightening on it, just light pressure and when re-installing the gas tube, use thumb and index finger pressure only. Hope this works out for you. Aif __________________ Cosmo the Lene,,, Smeller of old grease! http://i105.photobucket.com/albums/m...ber3575new.jpg

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