Strange chrono results

[Lebon]

Evening guys. So I decided today to put a 60 shot string across the chrono to find the sweet spot on my s510 ultimate sporter.
The gun is a .177 sub 12ft lbs and a couple of wks old, and has had a tin of pellets through it.
Filled the rifle to 190bar and the odd thing is the gun isn't producing a power curve as you'd expect.
The first shot was 784.1 and all the shots after this across the 60 shots decreased with the last shot being 675.1
I also own a s410 which has a power curve as you would expect from a non regulated gun, but the results from the s510 show a gradual slope decreasing with every shot.
Any help appreciated

[angrybear]

Sounds like a phone call to AA would be in order.