I can't say I'm an expert but I've loaded since about 1977.
Prairie Dog, I am not familiar with the optimal loading concept so can't speak to it.
I do think there are basic loads of a particurlar cartridge that tend to do well in many guns - safely.
Where it gets tricky is if your loads for your gun are at the upper limits in some manner: max powder, minimum bullet seating depth, minimal brass sizing.
For instance I have a 300 win mag rifle built by HS Precision. Its got a match chamber and long throat. My ammo won't even fit in most factory rifles because my bullets are seated out quite a way, and I only partially resize my cases. I also have a bit more powder in the case. I WOULD NOT loan my ammo to any other 300 win shooter.
Same for my .223 ammo for my Ruger 1 - again the bullets are seated far out beyond normal specs. in partially sized cases.
But if the ammo you build is well under max for powder charge and primer combination, brass is good and full length sized and bullets are seated into SAAMI OAL standards, I would think you should be ok and performance should be reasonably good. That's how factory ammo works so well in so many different arms.
You'd also want to know if the rifle for which the ammo is "borrowed" tends to show pressure early (tight bore and or chamber) or if it digests heavy loads easily.