QB78 End Cap OEM O-ring material used?

[iconoclast]

Does anyone know what the material/hardness for the original white O-rings used for the End Cap?
I know the tune guides state to use Viton, EPDM or urethane?
So far, I have tried Viton without much success.
The Viton I purchased swelled up and started crackling and popping upon removal.
I don't know if I got the wrong type of Viton or I got counterfit Viton.
I guess I will try EPDM next.
That's what Archer Airguns uses.
Also, O-ring/Seals 101 by Tim McMurry recommends urethane.
I'll try that too.
But, it would be nice to know what the OEM O-ring material/hardness is.
Thanks.

[CharlieDaTuna]

Urethane is the only way to go and if I remember correctly, it is 90 Durometer.

[iconoclast]

Thanks for your reply.
I also want to thank you for the extremely well written and easy to follow tune guide for the QB78.
I really had a lot of fun tuning my QB78 using your guide.
Your tune tips made a big difference in my QB78 performance.

[JDnearAC]

AS568A Dash Number
 113
 
Type
 O-Ring
 
O-Ring Type
 Standard
 
Cross Section Shape
 Round
 
Width
 3/32"
 
Actual Width
 .103"
 
Inside Diameter
 9/16"
 
Actual Inside Diameter
 .549"
 
Outside Diameter
 3/4"
 
Actual Outside Diameter
 .755"
 
Material
 PTFE
 
Durometer
 Extra Hard
 
Durometer Shore
 Shore D: 55
 
Temperature Range
 -100° to +500°F
 
Color
 White
 
Specifications Met
 Not Rated
 
I had the same thing happen to the viton o-ring in the cap, it was soft and looked about 3 sizes to big. When I heard the popping I didn't know were it was coming from at first. I am going to try these WHITE PTFE o-rings I'll let you know how they work out. They are rated excellent for resistance to abrasion and every chemical, oil, and gas listed on the Mc Master Carr chart.