this won't increase your air ranger dramatically in power but it can be handy to adjust into a smaller specific power range, my AR80 is tuned to 60fpe. I cut the coils of the main spring of the AR80 to drop it significantly(cut the coils as small as you can) and then played with this to fine tune.
the variation between the hammer striker being fully extended(to within 3/4 threads) and being fully retracted was 8-9fpe from memory...nothing dramatic.
If you are happy with your AR, I advise not to touch it and leave it alone.
I had to do mine as at 80fpe(version I bought) it was simply too much power for the .25 30.7grain extra heavy barracuda and putting the barrel back on with equal pressure on all 6 screws and the band without drooping or putting undue tension on one part is a real PITA.
I would also warn that the screw threads are easily worn so with all those cautions, proceed at your own risk, if you screw up your rifle don't come running to me.
one air ranger
1/16 allen key to remove the three screws on barrel band, either side of band and underneath ( I leave the band on as it's easier to support the barrel when removing the 6 screws below)
be sure not to misplace one of them as they are minuscule
remove the 6 screws - left to right I used a torx10/flathead/2.5mm allen key - the threads are easily worn so take your time, these might not be the right ones for 'new' screws, mine are badly worn and looked for the best fit to avoid further stress...I guess they are aluminium.
remove barrel and barrel band
remove the stock - 3/16allen key
down to this
2 screws to remove from either side, 1/16allen key, be sure to hold it tightly as it's under spring tension
this needs to be removed to get to the hammer striker - 3/32 allen key
when you put this back into the rifle when you reassemble you will need to pull the trigger to allow it slide back in.
unscrew this to allow the adjustment of the hammer striker 5/64 allen key
1/8 allen key to adjust the hammer striker
power increase, move hammer striker in.
power decrease, move hammer striker out as can be seen below I've moved it out 2/3 threads just to illustrate.
measurements I'd been asked about before
Not up to Stuart's quality but it gives those that had asked me this a better idea.