Shoot it first!
It might be a good shooter right out of the box, and too many of us myself included tend to try and make it harder than it actually is by fixing something that isn't broken.
If you take it a step at a time instead of trying to fix everything at once you can pinpoint the problem fairly easy.
Cleaning the bore making sure you don't have factory residue or any oil left in the chamber or on the latch shelf will go a long way to seeing how accurate it shoots.
Also make sure all you scope mount screws are tight, and that the rings on the scope are tightened.
Be aware that each gun is different, and the ammo choice and weight of the bullet make a huge difference in a lot of .243 rifles that seem to be more picky than other calibers.
Fortunately the cheaper manufactured brands seem to shoot the best out of the Handi's.
Let the barrel cool between shots especially with the .243 standard contour barrel.
That alone will let you know if you have an out of the box shooter, in Handi Rifles 101.
You've chosen a great caliber so have fun!
