Sorry about the confusion. I meant a sandwich stack but with the lug on the breach just entering the hole on the valve so that the entire stack is captured within the confines of the hole

In your first picture it looks like the oring is just proud of the valve and thus the lug is sitting above the socket hole.

In my experience of rebuilding crosman rifles of this type the lug normally just enters the socket....However, it may not be so in this version