The advantage in range between models often has to do with it having adjustable sights that allow it to be easily sighted in for the different points of impact along the trajectory path of the projectile.
Fixed sights aren't very easy to adjust for various distances and projectiles.
Dixie sells the Investarms .54 Hawken that's from the same maker as the Lyman guns.
It has a 1 in 48" twist, ~29" barrel, double triggers, an adjustable rear sight and a Monte Carlo cheekpiece. It's a very comfortable gun that's an exact clone of the Cabela's .50 Hawken.