Thanks for all the replies everyone.

On closer inspection, it does look like the underlever has been shortened, probably when the venom silencer was fitted.

Internally all is ok, no tight seals, lubed properly, spring kit is a wonky donky one.

So I’d guess that the problem is the shorter underlever

Don’t get me wrong, it’s not unusable and it shoots very well, it’s just a shame that it’s heavy to cock and it spoils it a bit...I wouldn’t want to plink all day with it if you know what I mean...

Would it be worth trying a different spring?, as mentioned before I don’t mind dropping power somewhat.

Paul