Wrong.Its not that the muzzle climbs before bullet leaves...thats not it. The lighter loads go slower. The sight plane is flat. Each bullet is arcing. Most likely they are both still arcing upward above bore line to target. The slower one has more time before impact to arc up. The faster one would likely hit higher as well if given same flight time before impact. Shorter time lower impact with the faster traveler.
Wrong, wrong, wrong.
A bullet fired out of a barrel parallel with the ground will never “arc up”...it will only drop.
Recoil does, in fact, play a part in where the bullet impacts.