Another thing, don't be surprised if 150's and 180's don't shoot to the same point of impact.
You seem like you are trying to get 150's and 180's to shoot identically for the same gun. You probably can get them close. Maybe bump the 150's up a little bit in velocity and they will match the 180's pretty close. You can play with ballistic coefficients and velocities and make them match.
But you will still have to sight in when switching from one to the other, and real world results may not match computer plots. Bullets companies have been known to fudge a little on ballistic coefficients.