For my part, any ammunition I bothered to buy in bulk is what I ended up setting optics to and leaving... since any situation where I'd need to dig deep into the reserves I'd want to run my 'A' game setup, I see no reason not to run 75gr/77gr out of my MK18 upper (and every other). The bulk M193 is for classes, practice, goofing around, and every other AR I've accumulated. Practically speaking, 75gr PPU has been cheap enough for me to just run that as the bulk version, and it's not terrible performance-wise if that's what I have on hand loaded up.

Last I looked, the 'right' answer would be something like 70gr TTSX to maximize terminal performance across the range of possibilities, but anything is better than nothing, and shot placement >> anything else, so having an optic that hits POA/POI to where you can drive it is the best answer, so picking one answer is going to be better than being spread across the entire option range.