Yeah, lookee there. You're smarter than you thought.
I've always stayed within the parameters of what a gun & cartridge was designed for.
I figure if I need a .300WinMag for hunting or something---
I'm better off buying one instead of trying to make my own from a .308.
Researching what other hand loaders have done and had good results with gives me good starting and reference points.
It is also certainly cheaper than doing all that research and testing on my own.
Ammo makers tend to take their factory loads up as high/fast as they can get them and still be fairly accurate.
I've noticed they go a little past what is actually the most accurate loading, and get right up to the edge of over pressure.
Most retail customers only look at the advertised speed of their ammo rather than what is most accurate.
Another thing is wear and tear on your guns. They are like any other machine-- they wear out and break eventually.
I look at it like the family car: Sure, it'll go 125 miles an hour.
However; it will probably live & last a lot longer if I keep it under 80.
Not too long ago, I fell into a unfired 70s era Colt rat gun.
I like shooting it, but not at the longer ranges. (the older I get, the less I want to walk down to distant target boards)
I load my .223s for it with 50 or 55 grainers at about 75% of the max for the above reasons.
The target Cong will drag off their wounded,,,, but these still hit hard enough for a clean kill on those little black dots.