I have an older Leupold prismatic bore sight that still gets the job done but it will only work with scoped rifles.
Strongly agree with 25 yard sight-in. Get a decent ballistics chart for the round you’re shooting and it should show relationship between 25 and a zero “way out there”. Back when I varmint hunted a lot we always sighted in for dead on at 250, that put as, as best I remember, 1/2 “ high at 25. If you 25 yard group was where you wanted it you’d be dead on at 250 and a bit low at 300