Rugers are more senstive to action screw torque than most. Most guys report better accuracy by loosenig all screws. First tighten the front screw as tight as you can possibly get it. Tighten the rear screw almost as tight. The middle screw should be snugged up just tight enough so as not to fall out. I've read of some improvement after this. Worth a try.
I'd try some different bullet weights and different factory loads. Also, if it is a new rifle it will shoot better after it's had had several boxes of ammo shot through it. Don't give up too soon.
Rugers aren't known as tack drivers. I've only seen 1 that would consistently shoot groups of around 1/2", but I've also never seen one that was worse than a 1.5" gun either.