My point Gerit, is knowing all the parameters for the use is very important. Improvements happen all the time, that's how we went from leather to synthetic seals ! When CDT responds to a post, he is offering information gained from years of experience and experimentation. I hold that experience dear to me, and would never discount it for someone that is not an experienced Airgun Smith.
You, and anyone are more than welcome to experiment, as I myself and many do ! And your successes will be greatly appreciated. I'm just trying to point out, that he, your friend, may not realise all the crazy parameters that are found in the humble airgun.
I didn't post to put you down, just to point out the variables in the airgun, and how golden Bob's guidance is.
Bill