I found the same thing in my reading on Mac brown, the oring was out of order.
That's the way I got the gun.
If your pic shows the order of how you had it assembled, the power tube oring should go behind the little spring.
Newer Level 7 valves
I picked up 68 automag in '10 from a kid that didn't know what it was. I attempted to set it up as a spydermag, but lost interest after purchasing a