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Thread: No substitutes: Polyurethane just can't be replaced.

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  1. #1

    No substitutes: Polyurethane just can't be replaced.

    Tags: Can I use butyl nitrate o rings o-rings orings instead of polyurethane automag AGD

    Anyways, I had a terrible leak down the barrel, turned off when the trigger was pulled, changed the power tube spacer (o rings .010) multiple times (.220 .225 .230), and nothign worked. I was using butyl.

    I switched it out with some 5 year old polyurethane orings i had laying around. BAM leak gone.

    I also noticed that polyurethane was important for the regulator valve pin assembly (.006). I got it to work with butyl - eventually, but I feel poly would have solved all the problems.

    So, I think the point of this thread is people should mention what parts of the valve simply can't be replaced with butyl - which is becoming more prevelant and polyurethane being more rare.

    Also, people should mention what sorts of local stores carry polyurethane!

  2. #2
    I've got nowhere close to me that I know of that carries urethane o-rings. I have to order them from McMaster or get them from AGD kits.

    Buna-N o-rings are all over the place though.

  3. #3
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    I order all my o-rings from my local hydraulics shop, I just walk in and ask for the sizes I need whether buna-n or polyurethane and it's usually in stock.
    A proud Canadian EH

  4. #4
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    Quote Originally Posted by halB View Post
    polyurethane being more rare.

    Also, people should mention what sorts of local stores carry polyurethane!
    They may not be very attainable at the local level, but AGD and Tuna both carry these in stock at all times. The problem is that people don't want to pay the price. It irks me to no end when someone spends $500 on an Emag and *****es about having to spend $30 on an O-ring kit. Seriously.

  5. #5
    Quote Originally Posted by OPBN View Post
    They may not be very attainable at the local level, but AGD and Tuna both carry these in stock at all times. The problem is that people don't want to pay the price. It irks me to no end when someone spends $500 on an Emag and *****es about having to spend $30 on an O-ring kit. Seriously.
    Agreed.

    The 12 threads opened this week could have been mostly solved with one new factory rebuild kit.

  6. #6
    Quote Originally Posted by OPBN View Post
    The problem is that people don't want to pay the price. It irks me to no end when someone spends $500 on an Emag and *****es about having to spend $30 on an O-ring kit. Seriously.
    Well you've got to admit, an Emag at $500 is a steal. An o-ring kit that contains about $7 worth of o-rings at $30 isn't as good of a deal, especially if you can get the one o-ring you need locally for $1 or less. Paintballers who buy pretty much everything except paint on the used market tend to always look for ways of making things as cheap as possible.

    Now I'm not knocking Tuna or the AGD store at all. I've placed orders with both on multiple occasions. But there's a reason people post WTB threads in the BST looking for things such as sears and pins, field strip screws, etc., just like there's a reason people sell those items in the BST too.

  7. #7
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    I live in BFE, so the chances of me getting poly o-rings is nil. My point is more along the lines of people not wanting to spend the money to do it right. If you have invested $500+ in a nice marker, don't be such a tightwad about spending the money you need to buy the right parts to fix it correctly. People need to realize that certain Orings are used for a reason, not just for giggles. Same with using the right oil instead of spraying it down with WD 40.

  8. #8
    Quote Originally Posted by OPBN View Post
    People need to realize that certain Orings are used for a reason, not just for giggles. Same with using the right oil instead of spraying it down with WD 40.
    Now that I'll agree with. Quality in means quality out, and that goes for everything that enters the valve and marker. Pretty much, TK & Co. did the research and gave us a detailed list as to what needs to be your inputs when it comes to the valve, in order to maintain the AGD standard of quality. That means urethane o-rings on everything except the Emag quad on/off o-ring.

  9. #9
    Nobody has really defined what "do it right" really technically means, which I think is OP's original question. And it's not just AGD's nonexistent word for it, because they kind of overengineered all kinds of stuff.

    You want the urethane for the moving seals. The power tube o-ring is probably one of the more important ones to have in urethane, more so for LX bolt.

    For something that's static, like the outer on-off o-ring, I don't see why that one can't be buna. It's the inner one that gets the movement, and that's why that one is teflon. However, seeing as all that o-ring is doing is keeping the thing off until you release the sear, I don't really consider it that critical. It can leak a little bit, and all that means is your chamber gets a little more air, or your LX might start venting. Hell my current mag has a tiny leak down the barrel when I hold the trigger down. It's not like I run around with the trigger held down, so I haven't even bothered to change it out, and it hasn't affected me.

    The last time I saw a problem with that outer on-off oring, it was simply because the o-ring itself was badly manufactured -- there was a visible defect on it. Maybe the previous owner had recycled a Q/D o-ring and threw it in there in a pinch. So if you did see a problem with non-urethane, don't automatically assume it's just because of the material.

    What I have yet to see data on is how long the various materials actually wind up lasting in a gun. I think that's where you'll be able to really calculate the tradeoffs.

    Other nagging issuse to consider:

    If an o-ring maybe only lasts half as long in buna vs urethane in an application, but costs only 1/4 what the urethane one, do you come out ahead? What if the original lasts 5 years, and the buna lasts only 2.5, but you bought 4 for the same price? Some of the price differentials are pretty significant.

    I've also had a problem with urethane o-rings degrading by themselves over time. Look up "polyurethane o-ring shelf life". So you might stock up on polyurethane o-rings, and then 10 years down the line when you need to fish its replacement out, you find that the thing is all cracked and brittle already. Meanwhile a buna one was cheaper already and might have a shelf life of 15 years.

    I think this is interesting data to have at least on an intellectual level, regardless of how much money you fed into your gun already.
    "Accuracy by aiming."


    Definitely not on the A-Team.

  10. #10
    Quote Originally Posted by GoatBoy View Post
    ... they kind of overengineered all kinds of stuff.
    Does not compute. April fool's?

  11. #11
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    Quote Originally Posted by GoatBoy View Post
    You want the urethane for the moving seals. The power tube o-ring is probably one of the more important ones to have in urethane, more so for LX bolt.
    This holds for most things. The LX actually works really well with buna but it does wear out quickly. The softer buna reduces bolt stick issues due to having a carrier that is a tiny bit too tight.

    Quote Originally Posted by GoatBoy View Post
    For something that's static, like the outer on-off o-ring, I don't see why that one can't be buna. It's the inner one that gets the movement, and that's why that one is teflon.
    The teflon is in place because it doesn't harden when it freezes when CO2 passes by it unlike urethane or buna.

    Quote Originally Posted by GoatBoy View Post
    However, seeing as all that o-ring is doing is keeping the thing off until you release the sear, I don't really consider it that critical. It can leak a little bit, and all that means is your chamber gets a little more air, or your LX might start venting. Hell my current mag has a tiny leak down the barrel when I hold the trigger down. It's not like I run around with the trigger held down, so I haven't even bothered to change it out, and it hasn't affected me.
    It is quite critical. If this oring leaks it causes bolt stick issues. The tiny leak you hear when you hold the trigger is caused by residual pressure in the chamber leaking out past the carrier oring because the vent hole is really close to the bolt stem vent hole and you are using a perfectly fitting carrier. If you have shims installed, removing them will probably make the leak go away. It goes away when the trigger is released because the additional chamber pressure on the oring tightens it up.

    Quote Originally Posted by GoatBoy View Post
    The last time I saw a problem with that outer on-off oring, it was simply because the o-ring itself was badly manufactured -- there was a visible defect on it. Maybe the previous owner had recycled a Q/D o-ring and threw it in there in a pinch. So if you did see a problem with non-urethane, don't automatically assume it's just because of the material.

    What I have yet to see data on is how long the various materials actually wind up lasting in a gun. I think that's where you'll be able to really calculate the tradeoffs.
    Its not always about life of the oring. Urethane is stiffer than buna. If you look at the elasticity of the two types, buna has much greater elasticity than urethane. Urethane also has a larger pressure rating. If there are large gaps to allow air flow when a passage is opened, buna can get pushed out of place easily but urethane will stay in place. In these situations, buna will get pinched and leak.
    Except for the Automag in front, its usually the man behind the equipment that counts.

  12. #12
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    so what are all the sizes of the orings needed in a valve including the quad?
    My sydarm weighs less than yours!!!

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