.22 Condor breech O-ring, 7.8mm x 1.9mm?

[JamesD.]

Something that could measure glands would be great as old ones taken out aren't true anymore.

 

[shambozzie]

This may help.

 

[JamesD.]

Yeah I see #11 or 7.8x1.9 being closest. Might need to purposely swell some. 
A custom breech fit to a new barrel could fix any doubt as to if the seal could be any better.

 

[shambozzie]

You don't have to worry about seal. When the trigger is pulled the blast of air cause the orings to expand and seal . 

 

[JamesD.]

It's a #011 5/16 x 7/16 x 1/16 70duro