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Discussion Starter · #1 ·
I've found one or two mentions of this which indicate it's not a biggie, but it really bugs me. :-\

What causes operating rod/piston to rattle after ~750 rounds? I put it all back together after light cleaning (as if it needed it) and the rattle started. I disassembled and found it to be the piston.

A quarter of all my wealth to anyone that can tell me how to make it stop!!
 

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Discussion Starter · #4 ·
When I hold the operating rod/piston and shake it, there is a distinct rattling sound as if something inside has come loose.
 

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There are weights inside the piston.
The rattle is normal.
Some have unscrewed the piston from the op rod and lost the tiny weights inside.
There are some posts about it somewhere.
 

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Patient to Doctor: "Doctor, It REALLY hurts, but only when I do THIS!"

Doctor to Patient: "Well, stop doing THAT" ;D
 

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Sounds like you are talking about the weights inside the piston moving back and forth. This is normal, per numerous posts here as well as my own experience.
 

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There's not really anything that can come loose. The piston head is loctited with 242 and torqued on at 250 in lbs. The gas tube itself may be a little loose - there is a male notch on the gas block, which aligns with a female notch in the gas tube. If you put your barrel in without having the notches aligned right, you can ding up the corners on the female notch, which will allow a little more play in the tube. It will never be able to fully rotate, but the wiggling will increase some.
 

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Discussion Starter · #10 ·
The piston head is loctited with 242 and torqued on at 250 in lbs.
The problem is loose weights inside the oprod/piston itself. It's been mentioned that some have removed the piston head to clear the weights and I have no problem doing that. I just wonder if removing the weights doesn't unbalance the piston. Apparently the gun operates fine without the weights though.

After removing the weights, is torquing the piston head back on to the oprod important or can I just eyeball it?
 

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Why in the world would anyone WANT to remove the weights in the piston/op-rod??? The XCR operating system was carefully designed to function flawlessly WITH them. I am sure there are some problems the design team decided the weights would cure, and you as the operator may not even be aware of ALL the possible problems that may ensue. If I tilt some of my AR's up and down I hear the same rattle. Guess what, it's the sound of the tungsten weights rattling in the H2 buffer. Same concept.

Why F--- with success :duh:

MadDog
 

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Personally I wouldn't just go arbitrarily removing weights from the piston without having a complete understanding of the implications.
 

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Discussion Starter · #18 ·
What would be recommended as far as re-attaching the weights?

I don't understand the question.. You mean how to reinstall them after removal?
Well, essentially not have them rattle around. To do that, I would have to remove the piston head from the oprod and somehow re-attach the weights where they belong. The question is what would be the correct way to do that.
 

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Well, the weights aren't "attached" to anything. They're just loose in there.

One thing you could do is remove the piston and stuff a tiny bit of cotton or something to take up the extra space. Might make a difference, and it wouldn't hurt anything.
 
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