It’s back together and shooting well, I’ll have chrono it when it’s bedded in a bit.
New seal and barrel shims as the old ones looked suspect.
Discovered the cocking lever rivet was apparently a replacement and hadn’t been peened over it was just pushed in so I’m glad that didn’t walk out whilst I was shooting the gun when I initially got it, that along with every screw being finger tight, a tbt kit fitted completely dry and an oval piston and the trigger sear engagement screw completely backed off.
Makes you wonder what this gun has been through
All I can say now is the strange twang has gone, the trigger feels much better and the cocking is effortless
Fingers crossed