Level 7 bolt won't seal...

[nuclear zombie]

I recently picked a classic mag with a four star minimag valve . Aired it up and there was leaking down the barrel. No problem , checked the bolt and couldn't feel the bolt piston engaging the powertube o-ring. I thought that the spacer was too short and wasn't compressing the o-ring enough to seal around the piston. picked up a powertube spacer kit tried every spacer included in the kit ,no luck still leaking. after further investigation I discovered that when the bolt bottmed on the blue bumper the bolt piston was only a hair away from engaging the powertube o-ring.

did the minimag valve require a different spec bolt? (using a long nose currently)
is it safe to sand down the blue bumper?
what happens if you place the o-ring on top of the spacer, between the spacer and tip ?
anyone else have this problem?

[Muzikman]

First off, no, all the Level 7 bolts are the same. If it is leaking, you want to try a shorter spacer, not a long. Have you replaced the oring it's self? I would not bother trying to sand down the bumber as that will not solve anything. Make sure the bolt and/or sear are not wore out.

After doing all that, if you are still having a problem come back and I'll think of more things to try.

[Muzikman]

umm, I just noticed something in your post that I don't understand.

"what happens if you place the o-ring on top of the spacer, between the spacer and tip ?"

Do you mean the oring that is around the PT tip? There should not be an oring on top of the spacer.

The order should be:
A PT onring goes in first
Then a spacer (start with the shortest one)
Then screw on the TP tip and snug it down with a nickel (do not over tighten...just enough so it doesn't work lose).


The other than that, I would look to make sure there is not a crack in the power tube. I have seen this happen and it causes a leak down the barrel.

[nuclear zombie]

I'm assembling it correctly according to the agd diagram, and it really can't be anything to do with the actual o-ring . or spacer, no cracks . The powertube tip is screwed all the way down until it touches the stainless powertube. but the piston in the bolt is not reaching the o-ring under the spacer, I can tell this without the valve in the gun , after I assemble it I can take the bolt run it back and forth on the powertube and feel when it touches the lower powertube o-ring, in this case the piston does not touch the o-ring unless I remove the blue bumper.

Personally I don't it should affect the gun too much if I place the o-ring after the spacer , I'm just concerned if it could cause bolt stick.

[Muzikman]

The nature of the design you can not tell if it's hitting the oring without gasing up the gun.

I'll try to explain it.

In an automag the bolt acts like a cork and holds back the air that is in the air chamber. There are a few importany parts that are needed for this cork to work.

1. you need a bolt
2. you need the sear to hold back the bolt
3. you need an oring in the power tube to seal the bolt stem
4. you need a power tube spacer to adjust how the oring seals on the bolt stem

If all of these things are not in order or in proper shape it will not work. This is the one way that a Mag in a PITA. All the tolorances for everything have to just right or the gun will not work.

When the gun is gased up air flows through the regulator past the on/off valve and into the air chamber. Once in the air chamber gas tries to escape out the power tube. A properly sealed bolt will prevent this. While the air is filling up the power tube it pushes the power tube oring forward, as far as the power tube spacer allows it. If the spacer is too long the oring will never reach the bolt stem, it's it's too short it will force the oring too far onto the bolt stem (this will not cause a leak, but can lead to bolt stick, or at least slow bolt release). This is why a correctly sized spacer is important. This is also why you should use the longest spacer you can without it leaking down the barrel.


******Remember, all this is only true with the level 7 bolt. The level 10 works slightly different.


All that being said. Just looking at an oring is not a good indicator as if it's good. It could be slightly mis-shapen, the ID could be slightly enlarged, etc... Also, you said you bought a spacer kit. Which spacer are you using? I would start with the shortest and see if it stops the leaking down the barrel.

Also, if your bolt or sear is worn, it can cause the bolt not to sit all the way back. This can cause a leak also.

[nuclear zombie]

I didn't know that the lower o-ring was supposed to be a floating one . I was under the impression that the inside of the powertube was cut so that the lower o-ring would go around the piston of the bolt slightly, regardless of spacer. Also that the spacer was to cause a slight compression of the oring so that it sealed and compensated for slight manufacturing variations of the components.

oh yeah it originally came with the .215 spacer and was leaking . I'll just have to test around when I get more air and see what works.

[Muzikman]

Just to clearify, there is only one oring in the power tube.

The PT Oring goes in first, then the spacer, then the power tube tip (which has an oring on it).

The oring on the PT tip is a static oring meaning that it doesn't actually hold back air. It's there to create friction so the tip does not work it's self loose.

[nuclear zombie]

Just to clearify, there is only one oring in the power tube.

The PT Oring goes in first, then the spacer, then the power tube tip (which has an oring on it).

The oring on the PT tip is a static oring meaning that it doesn't actually hold back air. It's there to create friction so the tip does not work it's self loose.

yeah , I know :rolleyes:

[Dayspring]

Well, you had suggested that you put the oring in front of the spacer. That would've been bad. The gun REALLY wouldn't have fired then. the stem would never have cleared the oring.

[rb211]

Dont be so sure that the power tube o-ring isn't bad, That was the only o-ring I ever replaced on mine before I switched to lvlX, Mine looked fine when I pulled it out, but it leaked like a sieve. Try a new one in there.

[nuclear zombie]

Well, you had suggested that you put the oring in front of the spacer. That would've been bad. The gun REALLY wouldn't have fired then. the stem would never have cleared the oring.

actually it should still work , the length of the spacer (max.235) and o-ring(max .125) combined don't even get close to the minimum .70 stroke length of the bolt. oh and because i've done it before.

[Muzikman]

At best, with an oring in the front of the spacer you are going to cause bolt stock that you can do without.

[KayleAGD]

Check the depth of the power piston in the bolt or try a different bolt , some have moved foreward after breaking the weld causing bad leaks..

[Scott Hudnall]

I had a very very similar problem and tried all the power tube stuff, spacers, oring, etc etc etc.

The problem turned out to be excessive wear on an old sear. Pull the sear and check to see if the front area isn't too worn....like maybe the person you purchased it from took a dremel to the sear.

[KayleAGD]

oh yea ,, and the classic "what's a rail bushing ???"