The average shooter doesn't develop a load for a particular gun. The average handloader will do that, and not every handloader has the skill to really make a rifle sing with a bullet that is really picky about seating depth. Even if a handloader does have the skill, the rifle itself can be an issue if you want other functions like being able to load from the magazine.
I knew a Presidents 100 tab holder who had to change his seating depth every 500 rounds in his service rifle to keep the jump to the lands consistent with the bullets he used for the 600 yard line. That is not a "single load for a single rifle" that is continual load development to ensure maximum accuracy from a rifle as it ages.
Most High Power shooters aren't that picky, but when you are competing for the Presidents 100 tab, then you are competing against other people who are that picky. So then it pays off to use the best bullets perfectly loaded for your rifle. That being said, the AMU is using the 185gr Berger's for their M110 loads for service rifle 1000 yard High Power shooting.
Heck, some top competitors use a meplat uniforming tool which is advertised to take 2% off of the bullet BC, but give much more uniform BC as a result. For those shooters looking to drop from .6 MOA to .5 MOA this is a good thing. For the "average shooter" 0.1 MOA is meaningless.
Anyways, look at the loads that win matches. The only people I know who routinely use the 155gr bullets are Palma shooters for whom the bullet was designed based on international shooting competition rules.
Machine guns are awesome until you have to carry one.