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!
It's got what plants crave!
Quote:
Originally Posted by
athomas
The level 10 should not have any shims if it is working properly. The shims do nothing to prevent bolt stick. You only need shims if the bolt can't travel far enough to vent air to reset. The shims shorten the distance that the bolt needs to travel. If the bolt fires or vents at all, then shims don't help. In your case, they are introducing a slight leak when you hold the trigger. Yours isn't an on-off leak, unless it is leaking into the grip frame(in that case it would be a lower on-off leak).
Are we mixing up terms?
If my on/off *isn't* leaking, then with the trigger held down, I might get a short amount of air out the front as residual pressure leaves the chamber, and then it's over. There is no more air to leak out because the on/off has *shut off the supply of air to the dump chamber*.
However, if the on/off *is* leaking, then the dump chamber continues to build up pressure even with the trigger held down, and eventually gets enough pressure to get the bolt to overcome spring force, move forward a tiny bit and start venting. If it's not a huge leak, then it only builds enough pressure to vent instead of going into full auto, which is what I'm saying.
Quote:
Originally Posted by
athomas
It is a dynamic oring. The regulator piston moves back and forth each time the chamber empties. A proper fitting buna oring might work quite well here too, unless you get up to the rated pressure of the mag valve. At that pressure, the buna oring would distort and get pushed out the sides and jam the piston. Theoretically, this couldn't happen, because the over pressure release should open before that happens.
I'm not talking about that o-ring (although I'm tempted to try a buna in there as well) -- I'm talking about the big fat one that is between the regulator halves.
And the whole bit about 3000PSI input to the valve is definitely along the lines of overengineering.
Quote:
Originally Posted by
athomas
This one is actually necessary. The buna orings are too soft and would cause massive barrel wobble when firing the gun.
So at this point I have to ask: what's the difference between a 90 durometer urethane o-ring and a 90 durometer buna o-ring, particularly for TL barrel use?
Quote:
Originally Posted by
athomas
From a quality control point of view, it is less of a headache for the customer service department. Heck, I've even seen poor quality aftermarket urethane orings that didn't perform well, so don't think that its only buna that we are saying to stay away from. Good quality urethane orings have a better rate of success, plus it is easier for average users to source lower quality buna and really have problems than it is for them to source lower quality urethane orings. Generally, the urethane orings are better quality anyway.
This is the most believable and practical reason, and I believe it.
But it has nothing to do with a technical spec, and more to do with non-technical issues. Terminology matters -- instead of "lower quality buna", you could say, "out of spec buna". But that gets us right back to the question about "what are the specs"?
And the spec from AGD for, say, the power tube or on/off o-ring isn't "90 durometer urethane 010 o-ring".
The spec is, "AGD Part #00123". Which is a pretty crappy spec. Nowhere on AGD's site do I see them give specifications for any o-rings. (And yes, I realize this is no different from pretty much any other manufacturer.)
That's what leads people to blindly go, "You should use AGD o-rings because they're up to spec". And then faced with the question, "Wait, what's the spec?", the response is, "The AGD o-rings." Which should remind you all of a certain movie...
http://www.youtube.com/watch?v=-Vw2CrY9Igs
Without an actual specification (while all the stuff you say is interesting, it is all as equally hypothetical as anything that I say) or *people actually trying it out*, then we don't really know.
I wouldn't mind trying some of it out just to see.