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Discussion Starter · #1 ·
Hi. I am a new RFB owner and I bought it second hand. When I bought it the gas adjustment was about 27 clicks. I cleaned it several times but only the last 4-5 times I cleaned the piston with a bras brush. The first time I cleaned it the piston was very hard to take out. Now it is a bit easier. Started to shoot Tula 150 recently and I can not adjust the gas. Yesterday I just tried again. I started by removing the gas cap and shot one round. Not enough pressure. That was good in my opinion. Then I put the cap on and turned it two clicks only, shot another round and I had enough pressure to reload. So basically I have no way of adjusting the gas and the cap is barely hanging there. Any ideas?
I am cleaning it now after the yesterday range visit and I will not clean the piston to see if I can regain the gas adjustment range. I followed the video about the gas adjustment.
Thanks for any ideas in advance.
 

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When you shot the second round did the rifle lock open on the empty magazine? You need to keep closing the gas adjuster till it can just lock open on an empty magazine and then give it 2 more clicks.

if it did lock open on an empty, disassemble it and look for proper welds on the two tubes up inside the bolt carrier channel. The spring guide rods pass thru these tubes and the tubes compress the recoil springs. If one is broken, you only have 1/2 the spring force and will have way too much gas available for the available spring force.
 

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Discussion Starter · #3 ·
When you shot the second round did the rifle lock open on the empty magazine? You need to keep closing the gas adjuster till it can just lock open on an empty magazine and then give it 2 more clicks.

if it did lock open on an empty, disassemble it and look for proper welds on the two tubes up inside the bolt carrier channel. The spring guide rods pass thru these tubes and the tubes compress the recoil springs. If one is broken, you only have 1/2 the spring force and will have way too much gas available for the available spring force.

Thank you for your answer.

If I take the gas adjustment cap off the rifle does not lock open. The moment I put it back on and turn it only two clicks, to start at the least amount of gas going back, the rifle locks open.

I opened it up again just now and checked the springs. They are not broken and when I press them manually forward the tension feels like it always did, strong enough.

The difference from now and the time I bought it, and it worked, is how smooth the piston moves in the gas barrel. After I bought it and tried to clean the piston first time, before going to the range, I had a hard time taking the piston out of the gas barrel. For several times I cleaned it after that I just spayed Rem oil on it and let it sit like this until I finished cleaning everything else. Last thing, before putting everything back together, used a few q-tips and a cloth and cleaned the piston. After making sure it was dry I put it back in and reassembled the rifle. The last two times though I used a brass brush to clean the piston. After that the piston started to be easier to take out. It is snug but it slips easier. Even though the brass brush should not have affected it I am concerned somehow the surface of the cylinder is too smooth now and the rifle behaves like having too much gas at only two clicks at the end of the thread, before falling out, so there is no range to adjust the gas.
The reason I found out was last time I switched from shooting Tula 160 gr to Tula 150 gr so I tried to make sure the gas is set correctly. Now the precision of the rifle is not as good as it was when I had it working at 27 clicks. I will get some federal 150 gr and try it again. It worked very well with that at 27 clicks.
Thank you again.
 

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Need to see if your piston has rings.
Many guys here have had the same problem and removing the rings solved it.
Don't worry, most pistons on the RFB never had rings:rolleyes:.
 

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Discussion Starter · #5 ·
Need to see if your piston has rings.
Many guys here have had the same problem and removing the rings solved it.
Don't worry, most pistons on the RFB never had rings:rolleyes:.
I think it has rings. I am planing to go to the range tomorrow and try a different type of amo. Here is my uncleaned piston after the last trip to the range.

Thanks a lot for your help. It is great to have guys like in the community.


Piston.jpg
 

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I think it has rings. I am planing to go to the range tomorrow and try a different type of amo. Here is my uncleaned piston after the last trip to the range.

Thanks a lot for your help. It is great to have guys like in the community.


View attachment 44794
The three spiral things in the groove at the end of the big part are removable rings.
If you take them off carefully, they can always be put back on.
They seal the piston to the bore and sometimes work "too-good".
Try it without them and see.
Several guys had their overgassed condition fixed by leaving the rings at home, in a drawer:D.
 

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Discussion Starter · #7 ·
Hi.

Went to the range and tried Remington 150 gr as the the guys from Vault in Vancouver recommended, before taking a look at it. Same problem. Will lock back at maximum gas cap open. Took the piston out and removed the rings. Put everything back together and readjusted the gas with Tula 150 gr and it worked at +12. Thank you very much for your help.

When I opened it up to clean it though the piston fell on it own from the rifle. It is so loose. I hope the feel of some gas blow back at the range I felt a couple of times was not true. I will check next time.

The only question I have to find an answer to now is what happened to get here. It worked in the beginning at about +27 and all of a sudden it was overgased. Maybe I will never know.

Thanks again and I am grateful for your advice.

Cheers,

Sunny
 

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Hi.

Went to the range and tried Remington 150 gr as the the guys from Vault in Vancouver recommended, before taking a look at it. Same problem. Will lock back at maximum gas cap open. Took the piston out and removed the rings. Put everything back together and readjusted the gas with Tula 150 gr and it worked at +12. Thank you very much for your help.

When I opened it up to clean it though the piston fell on it own from the rifle. It is so loose. I hope the feel of some gas blow back at the range I felt a couple of times was not true. I will check next time.

The only question I have to find an answer to now is what happened to get here. It worked in the beginning at about +27 and all of a sudden it was overgased. Maybe I will never know.

Thanks again and I am grateful for your advice.

Cheers,

Sunny
In the break-in period parts that move get to mate with each other. The rings mate with the piston cylinder and leak less gas than when they were new.
That's what I describe as working 'too good'.
You can always put the rings back on.
Mine never had rings (2.0) and if I haven't let it get too dirty:rolleyes:, the piston will come out really easy.
 

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^Yes. the consensus is that if the bolt doesn't lock back on an empty magazine with the adjustment knob fully loosened, or taken off, then you have to take the rings off of the piston. After that most people set their to B+13 or above depending on the ammo. I've seen a range of B+7 to B+22 for most ammo. I'm at B+13 with Aguila 7.62x51 150g.
 

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^Yes. the consensus is that if the bolt doesn't lock back on an empty magazine with the adjustment knob fully loosened, or taken off, then you have to take the rings off of the piston. After that most people set their to B+13 or above depending on the ammo. I've seen a range of B+7 to B+22 for most ammo. I'm at B+13 with Aguila 7.62x51 150g.
Yea..b+13 is where my gen 1 Rfb is at. I shoot 168s from federal and magtec
 
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