Help tuning- <12 ft lbs. For those in the know

Hi there,

I know most of you are used to work on much higher power, i wonder if you could give me some advice with regards to setting a consistent power/speed for my needs.
My rifle arrived in uk already set up by Ed, at 11.5 ft lbs.
The hammer spring screw is almost all out, with about 3 threads still in.
I wanted to check its consistence so i chronoed it on several occasions.
My aim was to get 570 fps with jsb exact 15.9 grain, wich translates to 11.5 Ft lbs and thereabouts, which is a safe limit i don’t want to exceed.
Anything above 582fps would be above the limit.
I have found however inconsistence between shots, up to 20fps, so i’m obliged to keep the speed at 550fps, to avoid breaching.
550fps is too slow and it changes the poi a lot beyond 50yds.
The changes in speed occur both during the same refill, and from a fill to another.
I.e, i set it a 570 and i think i got a good consistence, then refill and find out 20ps dofference.
I don’t think temperature influences that much, as such changes can be seen in a matter of minutes.
I fill at 220 bar (my bottle gauge) which is 210 on the gun’s one.
I think the power is higher to start with and then goes down and settles at 170bar, but you appreciate police will fill at 200 and start counting from there!!
Initially i thought the spring was beddin in, and needed to be broken in before settling at its final elasticity, but i’ve shot about 2000 pellets and i guess i should have happened already (or do i need more?)
Im currently trying to make veeery small adjustments at time, rather then moving the screw too much, slowly incresing, let’s see what happens.
However i would muh appreciate your thoughts with regards on how to obtain the best speed consistence.
I hear you unscrew the regulator 1/3 of turn and then decrease the spring tension, i guess i should do the opposite, so that more power needs to be applied from the hammer to discharge the air. This way i can tighten the screw a bit more, as right now i think it is so decompressed that it doesn’t “get” or “keep” the fine adjustments i make to its tension.
I hope you know what i mean.
Anyway i would much prefer to find a solution without having to strip down the gun.
I thought wih a regulated rifle i should have not bother with this shite, but it now seems i can’t enjoy using it as im always there checking the speed.
That’s very disappointing i must say.
Any help appreciated.
Cheers.