Wow your doing very well with the smaller cailbers, Very impressive.
It's all about the bullet. If a bullet will go subsonic AND be stable, distance is just a function of how much up you have.
Some very fancy bullets WILL NOT. Some bullets don't in one rifle but do in another (that is so bizarre to see). The only way to know for sure is launch them.
With elevation being a limiting factor, at some point, going further is more stunt then aimed fire - more like directed fire. Wind drift the same thing.
But on a calm day, it sure is fun to see a puff on target after waiting 4 to 5secs.
I have a friend that shoots Blackpowder 45cal boomers in orig 1800 something or other rifles. He is pushing monster slugs over 500gr but at around 1000 to 1200fps.
At 750yds, you do not want to be standing there. given the crude sights, bullet and speed, the accuracy is stunning.
When I get some time, I am going to see how far I can push a 22LR. We know 300yds is no problem. Wonder what it will be like at 500m?
Should simulate shooting to a mile or more.
Oh, for those who will ask "how far is too far?" - the answer. When the barrel obstructs the view through your scope, that's too far
Jerry