Artemis P15 need a help

Good Morning im new to forums and if i did anything wrong sorry :)

Got artemis p15 .177 and the problem is

On 50 meters it groups just fine on 265-270 power setting, im getting about 15-18mm groups

But on 100 meters i have to incrase power to 285-290ms and it shoots 2.5mm groups.

Its annoying chasing the power on field. Its ok for paper shooting but not for pest control.

Tried jsb 10.34 h&n baracuda and baracuda hunters same results shoots like laser bit have to change velocitie depending on distances :(

What can i do to make the gun shoot on 1 power setting on any 50-100 meter distances?

Thank you for any help i will recieve :)
hey buddy ive got the same gun and I'm shooting 10.5grain bisley magnum 1.77 cal and they group very well, try some different pellets, you're gun obviously doesn't like the pellets you're using!!, sorry I can't help you anymore 🤝 hope thing's work out🤞