That is your answer. It should be noted, however, that the perception of recoil does not correlate directly with the recoil numbers. This is not an uncommon feature of human perception. For example, if you were to ask people to listen to a series of sounds and tell you how much difference there was between loudness, there would be a poor correlation between perception and sound energies. For example, double sound energy corresponds to a 3 dB difference. I think I've heard that the minimal difference in sound levels people can generally distinguish is about 2 dB.

Back to recoil. My .25-06 has about 12 LBS recoil; my .30-06 has about 20 LBS recoil. When I shoot them, they seem pretty comparable in magnitude (both rifles weigh about the same and the stocks are very similar in structure). My guess is the difference between shooting 150 grains versus 180 grains will correspond to a significant difference -- as much as 2 LBS recoil -- but not enough to be perceived by the shooter to be a significant difference. Probably shooting these loads in two identical rifles side-by-side (rifle #1 shooting 150 grains, rifle #2 shooting 180 grains) you might be hard pressed to identify in a blind test which was which, would be my guess.