A .243 will work fine for casual shooting.
However, bore life will be shorter than a .30 caliber.
I shoot a .300 Win. Mag. at 1000 yards.
In fact, I ONLY shoot that gun at 1000 yards, as it is a dedicated match rifle.
I don't shoot it much anymore.
I got bored with being able to virtually NEVER drop a shot outside the 9-ring.
I could shoot scores of ~190 (out of a possible 200) any day.
Problem is, in most 1000-yard match rifle events, you often gotta shoot a perfect score to win.
I've seen guys shoot 199-15x fail to win the match.
If you are going to shoot a variety of long-range distances with a scope, you are going to want to spend a LOT of money on the scope. Think $1,000 minimum. Otherwise, you will not achieve the repeatability of adjustment that is required for the elevation changes.
With my 1000-yard gun, I have a Leupold 24x fixed-power with a 20 MOA base. I almost never touch the reticle knobs. For wind shifts or minor elevation corrections, I just "hold off" the required amount. I can see the mirage really well with this scope. After shooting Service Rifle for so long its a trip to be able to make a wind corrections real-time through the glass.