I've a post running on the UK Chinese forum, I'm copying it here in case one of the members has a better way to Trim the FPE.
The thing to note is that because of the UK 12 FPE limit Im after 10.5 fpe not 11 +, I feel 10.5 gives a decent sort of safety margin to allow for temp changes and so on One more limitation externally accessible power adjusters (unless they just reduce the power) are problematic at best.
I'm finding it very fiddly to fine tune the power of the 79 I'm setting up.
As far as I can tell opening up the Co2 flow path to get the maximum efficiency makes it very very sensitive.
The exhaust port/transfer port is wider than standard and the and the hole into the barrel is about 4mm (it's a 0.22) wide and slightly over that in length. The valve has a longer softer spring fitted replacing the original one.
Taking out just one thin washer (0.45mm 0.020) from behind the hammer spring dropped the fpe from 11+ by a good 1fpe.
I can get fine adjustment by elongating the trigger block bolt holes and sliding it back or forward but I'm wondering if I'm doing something fundamentally dumb and just making things hard for myself.
So am I doing this wrong, is there a better way?
If you have a better way of fine trimming the fpe please let me know.
I know I could make a new spring guide/block that would give some adjustment but its a chunk of work when I only need the adjustment during set up. Any better ideas, is there some simple way to achieve this? Have I overlooked anything?
One of the members has posted this one :http://ukchineseairgunforum.myfreeforum.org/sutra109240.php#109240
it's good but I only want to adjust at set up time so I'm after something easier.
Many Thanks Ora