So, got it. Lighter bullet spends less time in barrel because driven faster than the heavier. So hits lower. Barrel harmonics.
But, the 150 is traveling slower, so it is spending more time in the barrel than the heavier one, yet still you guys are telling me that the heavier one is hitting higher because of barrel time being longer. Really?? Care to start over?
Oh man. You pretty much answered your own question and complimented what your being told while you were trying to be so condescending.
Your heavier bullet is leaving the muzzle faster than your lighter bullet as you said yourself, correct? That means it is accelerating quicker CORRECT. A heavier bullet, accelerating faster is going to impart greater recoil into the rifle, would you not agree? So while that bullet is in the rifle barrel for a shorter time duration it may be causing the muzzle to jump higher and/or quicker, would you not agree? I won't even go into which is actually in the barrel longer because velocity alone does not tell us that, it will depend on the pressure curve/spike. The faster bullet may actually spend more time in the barrel than the slow bullet.
Harmonics will also play into this but without us testing we can not confirm if they are contributing to a raised poi or if they are actually helping to reduce it.
And as for the theory that recoil does not happen untill after the the bullet has left the gun... Oh man.
Grab your favorite rifle, find a steel rod that fits the bore, prop your gun on a rest with that rod against a 3-400lb boulder, hide, pull trigger with a string, then wonder how your rifle flew across the field while the boulder didn't move out of the rifles way so the gas could escape. After all with that rod making the boulder an extension to your bullet, think of it as shooting a 2.75million grain bullet.
Why do you think light rifles recoil harder than a heavy ones shooting the same cartridge, expelling the same volume of gas at the same pressure?