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Umarex Notos O ring List- Lets put them ALL here

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EmptyTin_Tim

EmptyTin_Tim

Member
Dec 8, 2022
410
266
Midwest, USA
Okay guys I wanted to compile the O ring dimensions used on the Notos since I couldn't find a schematic. If there is one available please post it here.

In installing the plenum I was told by the plenum seller to check barrel o rings cause my FPS was lower than it should be. I found one article listing what size for OUTER o rings to get and I ordered them.

Notos barrel o-rings - Airguns & Guns Forum

Notos barrel o-rings , Air guns, Airgun Forum
www.gatewaytoairguns.org

They arrived and look like this
20230830_203914.jpg

The two vertical are OEM and others are O Ring Store. You can see the OEM are bigger ID. Yes OEM might be stretched but they definitely were chewed up from the factory hence FPS loss.

I measured the OUTER 2 barrel o rings here:
ID
20230830_205932.jpg

Thickness: 0.90mm
20230830_210441.jpg

And OD
20230830_210628.jpg


Okay then I took out the INNER 1 barrel o ring and measured that
ID
20230830_205231.jpg

Thickness
20230830_205406.jpg

OD
20230830_205659.jpg


If someone got different results let me know I'm not a machinist just a casual caliper owner lol

Please post the rest of the O ring sizes for whomever to use so we can keep these awesome Notos's shooting strong!
 
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Firewalker said:
The issue is that these are non-standard sized and not available for over the counter sales.

I got a quote on them from a manufacturer but the die alone was $500 plus $250 for setup and 25k minimum run. Just over $2000.00 to get a batch.

Sorry, no-can-do
Click to expand...
This should be the probe o ring (inner barrel), if I understand how to put the dimensions as this website has them.

https://www.theoringstore.com/store...product_info&cPath=368_12_38&products_id=1844

nervoustrig said:
The fill port O-ring can be replaced with a -008 in 90 durometer. The original is metric of course but a -008 is a good fit and more easily obtained for most of us. 90 durometer is important because the original is too soft and usually extrudes and fails before long.
Click to expand...
You know what I put that one in there but didn't want to have 2 variables (replaced outer 2 o rings that were actually chewed up but inner OK). Maybe I'll just replace the inner one if my FPS reads slow still.

The outer 2 I ordered in my OP are definitely smaller OD like how it is installed compared to OEM. The replacement o ring are more flush to the barrel OD than OEM. It slides into the receiver easier than OEM.

I will see if FPS reading improves. If it does I won't worry. If it doesn't I may have to do another order for larger OD but as Firewalker said the 0.9x 10.5 is a custom size not found on Oring store..
 
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EmptyTin_Tim said:
You know what I put that one in there but didn't want to have 2 variables (replaced outer 2 o rings that were actually chewed up but inner OK). Maybe I'll just replace the inner one if my FPS reads slow still.
Click to expand...
I was referring to the fill port. Based on your comments about velocity, I think you were referring to the transfer port.
 
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nervoustrig said:
I was referring to the fill port. Based on your comments about velocity, I think you were referring to the transfer port.
Click to expand...
Whoops sorry. I shouldn't speed read when this is this technical.

Yes. You are correct. I put that size in 90 Duro on that screw inside the fill port when I had the tube apart when installing the plenum. Thank you for that tip to use 90 duro. I think that'll easily last 2x longer than OEM. My OEM already had marks and it isn't super old.

I did try a different o ring in the transfer port (inside the breech of the barrel) though and decided even though it was similar, the OEM still looked OK so I put that back in.
 
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Tim,

My apologies for the bad information on the barrel tenon O-rings. Knowing that SPA calls out O-rings on their exploded drawings by the OD, against industry standard, I translated the callout to M0.8 x 8.4. However it looks like the translation had already been done, making my figure incorrect.

If it continues to be that no source can be found, the way I would approach it is to take an M1.0 x 10:
https://www.theoringstore.com/store...product_info&cPath=368_12_36&products_id=1770
…and chuck it up on a mandrel (dowel, transfer punch, or similar) and spin it up to abrade it down a smidge.

Taking off 0.2mm isn’t much. Granted it’s a thin O-ring so it will want to squirt around on the mandrel as soon as you apply pressure with the abrasive. Meaning it will need a very light touch but it’s feasible by holding a strip of sandpaper taut and bringing it into contact with the O-ring. Or if you have a rubberized polishing bit for a Dremel, you can spin it up and bring it in very slowly until it just kisses the OD of the O-ring. This approach is quick and easy, and has helped me out of many a pinch.
 
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nervoustrig said:
Tim,

My apologies for the bad information on the barrel tenon O-rings. Knowing that SPA calls out O-rings on their exploded drawings by the OD, against industry standard, I translated the callout to M0.8 x 8.4. However it looks like the translation had already been done, making my figure incorrect.

If it continues to be that no source can be found, the way I would approach it is to take an M1.0 x 10:
https://www.theoringstore.com/store...product_info&cPath=368_12_36&products_id=1770
…and chuck it up on a mandrel (dowel, transfer punch, or similar) and spin it up to abrade it down a smidge.

Taking off 0.2mm isn’t much. Granted it’s a thin O-ring so it will want to squirt around on the mandrel as soon as you apply pressure with the abrasive. Meaning it will need a very light touch but it’s feasible by holding a strip of sandpaper taut and bringing it into contact with the O-ring. Or if you have a rubberized polishing bit for a Dremel, you can spin it up and bring it in very slowly until it just kisses the OD of the O-ring. This approach is quick and easy, and has helped me out of many a pinch.
Click to expand...

That's what I've had to do on my guns, I'd really like to offer replacements.
 
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Firewalker said:
I submitted a request for 1000 o-rings for the barrel, we will see if these dimensions are stock or special order. Stay tuned...
Click to expand...
@Firewalker .. did you see the diagram of the notos #26,27 front sight.. it's what I was trying to explain to you.. you put a request in for the barrel o ring.. I assume that is the ones that seal barrel to action? 2 of them.. my notos came with a loose barrel and shroud and when I checked it had one complete o ring and the other one was crumbles.. since it's not very old and probably only 100 rounds.. must be pretty crummy o ring.. hopefully you can get after market o rings that are made out of quality and not trash..
Mark
 
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WOW so glad to see that diagram!!!@Raptor72 Did you draw that yourself? I haven't seen that schematic anywhere online.

nervoustrig said:
Tim,

My apologies for the bad information on the barrel tenon O-rings. Knowing that SPA calls out O-rings on their exploded drawings by the OD, against industry standard, I translated the callout to M0.8 x 8.4. However it looks like the translation had already been done, making my figure incorrect.

If it continues to be that no source can be found, the way I would approach it is to take an M1.0 x 10:
https://www.theoringstore.com/store...product_info&cPath=368_12_36&products_id=1770
…and chuck it up on a mandrel (dowel, transfer punch, or similar) and spin it up to abrade it down a smidge.

Taking off 0.2mm isn’t much. Granted it’s a thin O-ring so it will want to squirt around on the mandrel as soon as you apply pressure with the abrasive. Meaning it will need a very light touch but it’s feasible by holding a strip of sandpaper taut and bringing it into contact with the O-ring. Or if you have a rubberized polishing bit for a Dremel, you can spin it up and bring it in very slowly until it just kisses the OD of the O-ring. This approach is quick and easy, and has helped me out of many a pinch.
Click to expand...
@nervoustrig Absolutely no issues here man, I am grateful for the original o ring size suggestion because I hadn't ordered from the o ring store before but it helped me understand that process and I have put in another order now.

Here's what I ordered from there now
Screenshot_20230901_085738_Gmail.jpg


I ordered a few sizes around the measurements I took since unfortunately they don't have smaller than 1mm CS for the 10mm or 10.5mm ID. I ordered a few in 90 duro just cause but I'm thinking it won't be able to stretch enough.

I also got the 1.5mm X 5.5mm for the inside barrel O ring but they only had it in 70 Duro so idk how long that will last but at least I'll have spares.
 
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A few comments about O-ring selection as it applies generally across various models. For breech O-rings, occasionally the tolerances and/or part geometries will allow for a 90 durometer for better longevity. However it’s usually beneficial to have a little give to it so I expect the 70 durometer you ordered will serve you well.

Contrast that with a bolt O-ring where 90 durometer is usually preferable.

For barrel tenon O-rings, in most cases either 70 or 90 durometer will work perfectly well so long as the receiver is deburred well and lubricated with silicone. But 90 durometer will be more susceptible to getting a bite taken out, and the risk grows the thinner the cross section. O-rings in the -00x series (0.070” CS) or 1.5mm (0.059” CS) usually aren’t too bad but those with a 1mm (0.039”) CS frequently need careful coaxing to avoid damage when installing. And of course the tenon O-rings on the Notos are even thinner than that. Given the harder material confers no advantages in this application (not subject to abrasion or extrusion failure), 70 durometer is usually the better choice.
 
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