Changing manufacturers may cause your point of impact to be off farther than changing bullet weight from 180 to 150.

I typically shoot Remington (what is usually available, not necessarily the best). Geko or some other brands I've tried out, have a noticeably different muzzle velocity. My best results are my home loads, which I usually load near Remington specs.

I'm zeroed now with 168 grain, I can go either direction and not worry about my point of impact changing much at under 200 yards, if I have to use store bought ammo in a different bullet weight..

Usually IMO when point of impact changes drastically, it is a combination of factors, a little here and a little there adds up. Different bullet weight, stable rest, form and even weather add up.