after you take it out of the stock,
the hammer spring adjustment is the large silver flathead l,
it will only go out so far,
and will only go in so far.
the grub and screw hold a sort of spring guide that the spring fits over,
and turning the flathead pushes the guide forward to increase hammer spring tension.
BUT!!!!
even if you run the reg up over 150bar,
the hammer spring is too strong,
even backed out all the way,
so i took the small guide cup off the hammer adjustment and put the screw back in so it still had a guide,
this allowed the spring to expand another 1/8th inch or so,and in turn decrease the hammer tension slightly.
but with the "spring cup" removed there are no adjustments to be had,
so i just tuned the reg to the pressure that gave me a flat shot string,
(in .25 with the 25gn im right at 130bar)
its not a powerhouse,
maybe with a bigger plenum it could be,
i have the .25 barrel on it,
running the jts dead center 25.39gn,
and its pushing them to 830fps but the string is so flat.
reg takes alot of shooting to get it to settle down,
mine would creep nearly 20bar in 15 min
but its getting better now after 600+ rounds through it.