My .25 Prophet

Was shooting on my range this morning and knew the Prophet didn't have a full air fill. I got distracted concentrating on POI and what I was or was not doing that was affecting that. All of a sudden at 50 yds the pellet barely made it to the target. I went off the regulator. Not 20 or 30 bar. Just a bit lower than the reg setting. I've done this with other rifles and there was a gradual decrease in power and the shots started hitting lower. After a couple of low shots I usually dummied up and went for a refill. The Prophet seemed to say I will not work lower than the set regulated pressure.

This an anomaly?