I don't know. I wouldn't think a moderator would slow the pellet.
I was watching YT vid where a guy was tuning up a Hatsan 135 30 cal. One thing he did was pump up the gas piston to 150 bar. I seem to recall the piston was marked 'max fill 150, or 160 bat'. The factory fill was around 130 bar.
Anyways, after pumping it up to near max, he was getting around 590 fps with the JSB 44gr, and 550 with the JSB 50 gr.
