I'm keener than a headmaster with a cane to see some answers to that one too, I'm gonna guess that a quality muzzleloader rifle would be good for 300 yards. I'm equally as keen to hijack your thread and turn it into " Best western long range shots " She might not be a muzzle loader but check out Magnam PI as Quigley at work. https://www.youtube.com/watch?v=73hl--IMoWU and Billy Two Hats Fron the 7 minute point https://www.youtube.com/watch?v=wQczXLHmYWQ
Gun control requires concentration and a steady hand
Seymour Black Powder Club shoots to 600m with a full size buffalo plate. Chicken, turkey, pig and ram to 500m and they are HARD in the wrong light! Most use Sharps design falling blocks or Remington design rolling blocks. Starting calibre is 38-55. I use a 40-65. Would love to see a big 50-110 artillery shell!
There's still a few of Wile. E Coyote's ideas that I haven't tried yet.
In the mid/late 1800s a US shooting team out shot the vaunted Irish shooting squad at a match shot at Creedmoor New York. The US teams used two different makes of rifles Sharps falling blocks and Remington rolling blocks, all the American rifles were chambered for the .44-77 cartridge and the course of fire reached out to 1000 yards.
I've been asked: "How many guns do you need to have?" My answer remains the same: "One more."