Based on my Hw 80 with a light spring set up ,( just about as easy as a Hw95 /R9 ) and minor port work and cup seal doing a butter easy to cock 785 , with 14.6 Ftt. I’d say I could easily get 675 with 20 grain domes. I tested many springs and all big tune kits were horribly over sprung in my opinion. Then again I don’t drop kits ,I rework the gun for its piston stroke, barrel length, piston weight,port size and spring load.
I tested springs from .148 which is factory wire @ 30 coils depending on how you count, to narrower Macarri power springs and Vortek. They both go about it differently and still get results. I saw 835 to 850 14.6 ftt, with my work and those springs
that being said ,,,,they were not pleasant to cock.. nor to my liking. (If I need big game break barrels ,I go to my other long stroke built guns) ,,,
in most of my tuning I’ve seen a 90 to 100 fps decrease going from .22 14.6 to .25 20 grn ftt .. I’ve got a Uk Built hybrid Tommy shooting 25.3 @610 and it’s my 40 yard gun with no holdover sighted at 25 yards
The 30 mm tube will help with not heating the air so fast ,but because it’s a short stroke it’s a real balance game. I’d love to play with a .25 HW 80
they are my new love affair in .22.
