My 90 is FAC, actually runs @19FP, but have tested it from 15 up to 21..same story. Completely inconsistent.
Sometimes there are some good spots, but nothing special, average groups are always 1,5-2" (with the best pellets..).
Belive me when I say I've tried everithing: seals, gas ram seals, schrader valve, muzzle recrowning, barrel joining new washers, lapping the barrel and so on. Also tried a new barrel of same caliber...
Tested also a couple of different 90 same caliber but no difference.
I know about the recoil management, ma dont think this is the issue (I've a bit of experience, owning many other FAC airguns: Eliminator, Patriot, HW80, Diana 52...).
Really I think there are no other things to do..., except to test a new barrel, meaning a different kind of barrel. For this reason I was thinking on polygon, or may be at the Taylor's smooth-twist...
In my experience, the only springer in 25 that is capable to shot good groups at FAc levels (18-21FP) is the Diana 48/52; with a good tuning kit prints 1,5-2" at 50 yards...
So, make this rifle shooting better groups is becaming a real challenge for me.
every suggestion is well accepted