One of the things I don't like about those scopes -- they make people think that 150gr is a good load for your gun. I have never owned a gun that was accurate with the load that scope is set up for!!! Apparently you don't have one either.

Cut your charge to 2 pellets or 100gr loose and try again. If not, try a 300gr bullet as you can keep the charge up but velocity down, and sometimes the velocity is the issue.

Yes, 120-125gr loose is roughly equivalent to 3 pellets.

If it is hot out, let the gun cool at least 3min before reloading, heat softens the sabots and ruins accuracy.