Hello all. One more time- thank you for opening this thread and discussion.
Encouraged by your experiences, I felt ready to go down this rabbit hole and start playing with the HS tension. Right from the start, the results are beyond any reasonable expectations.
So, here we are:
I have U2 .25 700mm, using 37gr (2.4g) Zan slugs @160bar approximately (1/4 turn CCW on regulator from factory settings).
Velocities before HS tuning were 938-946fps with approximately 40b airdrop for 1 magazine/ 10shots. That’s 4b per shot.
Encouraged by your posts, I turned my HS screw 2 1/4 turn CCW, because of that I had to dremel the stock interior for approx. 1.5mm. I fired 10 shots, then waited for 24hours, then fired another 20shots.
To my shock, on first magazine speed started at 475fps, but next day, on second and third magazine, it went all the way to 715fps. But ofc I wasn’t satisfied with that and I started to turn HS screw CW. At the end, for 3/4th of a turn. So, now my HS screw is 1 1/2 CCW opened from the factory settings.
I shot 1 magazine, then waited for 24 hours to allow the spring to adjust and then again, today, I shot 1 magazine. So…
On my last magazine, 10shots, speeds were from 920.6-926.5fps, so my ES was less than 6fps (before this tuning, usual was 8-10fps, if I remember correctly max ES was 12fps AND… now the airdrop per magazine (10shots) is approximately 15bar



DAFAQ?!?
So… next thing I’ll do is to play around this setup.
My goal is to leave the regulator @160b, to find minimal tension for HS while achieving speeds from 900-1000+fps, depending on slug grains, while using minimal air pressure possible what would also be quieter than it used to be.
As for precision- I was focused on velocity/air pressure but I haven’t noticed any noticeable precision drop while doing so.
Guys, one more time big RESPECT

, this was unbelievably well spotted detail in these overall fantastic airguns.
Thank you again,
S.