TargetTalk

Greetings,

Im sorry that my first post in this forum must come as a question but i really havent a better ideia of what to do.
The O-Rings on my TAU 7 that relate to the CO2 Canister have been over a lot of stress and now on the next canister change the o-ring will shred.
Does anyone have a relation of all the orings on the TAU-7 so i can get a replacement one ?
I just need the specifications :(

Thanks for your time reading and helping :)

Francisco

I _think_ they are 2.5 mm x 14 mm, but I'm not certain. I've also ordered some 2 mm x 14 mm O-rings, but I don't think they fit right & I had to order the thicker ones. I've ordered them from McMaster Carr in the US. The 2.5 mm thick rings were ordered more recently, which is why I think that is the correct size.

The standard black O-rings that BRNO used are Buna-N Nitrile material, which absorbs some CO2 under pressure. If you remove the filling cap immediately after having the O-ring under pressure, the CO2 can't escape quickly, and you get gas bubbles in the rubber. It's similar to divers getting the "bends". Eventually, this will tear up the O-ring.

The one thing you do NOT want to do is to re-use the same cap immediately after changing the cylinder. When you screw it on, it will chew up the swollen O-ring and destroy it in short order. This is why the pistol comes with two caps. You need to alternate them so the O-rings can recover between uses.

A better approach would be to use silicone O-rings, which don't absorb nearly as much CO2. They are more expensive, and much harder to find in the specific size required. Walther used to use silicone O-rings in their CO2 guns. The last time I looked, I couldn't find anyone willing to sell reasonable quantities of the Tau-7 size O-rings in silicone.

Thank you my friend. i will try :)

here: http://www.mcmaster.com/#o-rings/=429jbw

They carry O rings in many materials and sizes.

Those green o-rings you may have seen on Walther CO2 guns are polyurethane - much more tear resistant than silicone. The trick is to find them in metric sizes!!

That shouldnt really be a problem in Portugal :)

ghilt wrote:Those green o-rings you may have seen on Walther CO2 guns are polyurethane - much more tear resistant than silicone. The trick is to find them in metric sizes!!

Quite right. That's what I get for spouting off from memory. I think polyurethane O-rings (if you can find them in the correct size) are the best "cheap" material. There are more exotic materials that are even better, but may not be worth the price. Viton O-rings are available in the correct size from McMaster Carr, but they cost about $.60 each, vs $.08 for Buna-N material.

Viton, with its low pearmability and good compression set resistance is great for static seals. Viton seal life, when compared to polyurethane, would be much shorter for cylinder sealing applications where abrasion with the threaded section of the cylinder probe or gun receptacle would tear the o-ring.
The price of OEM o-rings is such ($5 to $10 a pop) maybe we can convince this thread's initiator to be a source for our importing (LOL).

you can find all kinds of O-ring at www.smallparts.com

Different material, different metric sizes.

They are the supplier for research lab parts.

Great source for all kinds of stuff and fast delivery. Too bad it doesn't have a good SEARCH tool.