Tuning FX Crown MKII .25cal - observation

[Corvid_hunter]

I took my MKII Crown (600mm barrel) out last night after switching from the pellet port over to the slug port. Prior to the switch I noticed that I had similar FPS on Medium and High on the transfer port setting. Now there is a difference between the two and an increase in FPS on High. The factory tune came with the reg set at approx 115 bar. I increased the reg to 125 bar and lost velocity. I assume the factory tune is fairly efficient, for a factory tune. It's topping out around 860fps and I know I should take it out of the stock and increase the hammer spring tension, and pick up the reg so I top out around 925fps, but it is very accurate as is and I'm wondering if I should just leave it alone.

 

[Corvid_hunter]

Went out today and started decreasing the reg pressure to see what would happen to the velocity.
- 115 bar was 825fps.
- 110 bar was 853fps
- 100 bar was 906fps
- 98 bar was 905fps
- 91 bar was 898 fps.
I'm guessing by the slight decease in velocity at 91 bar, it's a good tune for the current hammer spring setting. I think my reg gauge is off by 10 bar or so because on my last group it looked like it went off the reg at about 110 on my tank gauge.

Both groups (left and right targets) are 5 shots at 30 yards.

 

[Glem.Chally]

Looking good

 

[Corvid_hunter]

Thanks. I don't think I want to mess with this factory tune.