Tuning Loss of velocity next day after tune

[poof]

Hello all,

Been lurking here for a while but just registered. Reason being, I need some direction.

Recently acquired an FX dreamlite compact in .22 and after a few short weeks, decided to upgrade some internals which include huma air high flow transfer port, matching pellet probe and hammer spring. Proceeded to re-tuning the gun to the desired velocity for projectile: at around @860 fps (avg 864 fps with 9fps extreme spread and 2.7 standard deviation) which I found to be a real sweet spot for my rifle with the JSB hades and regulator set to ~130bar

This was done yesterday, I was really happy with the tune. However, today I test it again without touching anything in the setup and suddenly the velocities dropped by about 120fps in the 745fps range with same projectile and regulator gauge showing the same pressure.

Temperatures are roughly the same, no significant change so I'm extremely puzzled by this.

Any input or suggestions would be much appreciated. TIA

 

[Vetmx]

Make sure your transfer port wheel didn’t rotate slightly. Make sure your probe is tight. Lastly, check your transfer port oring. 

 

[elh0102]

If the reg gauge is accurate, and there is not a sudden leak, then it seems to me that the HST is the other big variable. I would play with the spring tension again to get back to your target velocity, see what happens. It's not unheard of for the spring to settle a bit, depending on the finishing of the end coil, and the surface on which it mates. But your variance seems a bit extreme for that issue.

 

[Airgunmann]

Did you try the speed of several shots or just once if it was just once possibly a double feed or bad Chrono reading weird