Kalibr cricket mini carabine wst .22

Welcome on-board! I have the same gun. I usually shoot about 4 mags on one fill from about the same PSI. Your millage may vary a bit, I would say to play with it and look for POI drop and take note of the pressure at that point. If you don't already have one, a Chrono may be a good investment. Mines shoots JSB 18s at about 850fps and the 14s about 890fps. 

4 MAGS ERIC

Most Crickets have regulators so the pellet speed should have an average speed spread of under 20 fps. Mine has an average speed of 880 fps. Once it falls off the regulator the pellet speed will rapidly reduce. Not sure if the mini has a smaller reservoir but my standard carbine gets 4 mags per fill. Once your POI drops you know you are off the regulator and need to refill. Crickets are very accurate guns! They have a hammer-forged barrel so if your groups start to open up better clean the barrel. 

A chronograph is the best accessory investment one can make. It helps one diagnose a lot of issues with our equipment.