Air Force Texan LSS bad seal?

[kcatx]

Looking at my new LSS it appears I have a busted o-ring on it-- yet I can't see where that o-ring would actually seal anything. 
Can somebody tell me what the deal with this is?

Thanks in advance.

[ShakySarge]

That appears to be the "breech seal". Not sure what they actually call it though. See photo and look in the same spot on yours. I am almost positive that is what it is. Call AirForce to get a new seal probably free of charge as well. Man I need to dust that thing off!

[kcatx]

Thanks ShakySarge!   I just called them and they are sending me on.  It's called the "valve buffer oring".  I asked what size it is because I have 2 assorted boxes of orings sitting in front of me but they said they couldn't give out that information!   Oh well, c'est la vie!  I'll have it in a few days I'd guess and see what it matches up with. 
Thanks again!

[ShakySarge]

Excellent! I suggest measuring it when ya get it to buy spares elsewhere and let us know what size it is.