With reference to the hammer spring adjuster:
A good place to start - with the highpoint of the adjuster knob cam interfacing with the adjuster screw' head, adjust until, with the action and barrel pointing up, you can just see the hammer head appearing in the peephole that allows you to see the head of the valve stem in relation to the hammer head. Tip the barrel down and the hammer will drop into contact with the valve stem head with an audible "click". Tip the barrel back up and it may click again and you will see a gap appear again.
Now for maximum power according to the other settings, that adjustable gap has an optimal value/separation.
If the gap is too narrow, or disappears altogether, the power will go down and the knob adjustment loses value between some settings.
The optimal gap will be found somewhere close to when the hammer head is just visible in the peephole with the barrel pointad up.
The reason for this is to be found in the fact that FX has been using for many years what has more recently been "discovered" as the "free flight hammer system", by whaterver name,
In fact the FX 2000/Excalibre/Tarantula had the potential to be set with no hammer spring pretention and a gap 18 years ago yr 2000. Hammer bounce elimination and therefore potentially excellent air efficiency was the reason. Later the Royale series and now the Crown and Impact have it incorporated.
So if you desire optimal power and efficiency that is a good pace to begin. I have my .25 Crown set to give from 54 fpe with 33.9 gr JSB on Max and TP 3 all the way down to under 15 fpe with 25.4 gr Kings or Polymag bird busters at Min knob adjustment and TP setting 1 (mine is an early model) with reg set at 130 bar.
Not sure any of this helps, but I don't see this explanation in others' posts/videos. Best regards, Harry.