To shoot a fox at any distance with any rifle, the first three things you need to know are;
- What distance the rifle is sighted in (zeroed) at.
- Where the bullet will hit, higher or lower than the cross hair in the scope, at various distances within the effective range of the caliber you are using.
- What distance the target is from your firing location, therefore knowing where the point of aim is for bullet placement for a quick humane kill. Therefore knowing the amount of hold under or hold over required.
The illustration below is a clip taken of an interactive website that allows you to understand the trajectory and wind effect on your shot. It could be argued that the .243 Win is an effective caliber on foxes out to 350 yards if the above 3 points are established.