If what to take long shots nothing short than 20 inch, as for caliber I stick with something you already own for be 223or243 because I rather have 2 or 3 guns of same cal than 7or8 of all different but that’s just me
I have a Alex pro AR-10 22-250. 24′ semi bull barrel with a Nightforce NXS 5-22. I have not shot it much because i had a neck surgery backed up by a back surgery. they are also chambering all of the Nosler rounds and 7mmRem mag and 300 WM.