What model is it ? Rugers are really picky about what they shoot, try some CCI, Remmington or Hornady ballistic tips. Have you checked everything to make sure its tight, bottom metal, scope rings ect ? If you are still having problems there are several things you can try. First bed the action and float the barrel if it isnt all ready, the all weather and VZ should already be but you can run a dollar bill down it to check. The standard 77/22 with a walnut stock will have a pressure pad towards the end of the barrel between the barrel and the stock, sometimes moving it around until you find the sweet spot will improve you groups. I just find it easier and more effective to float them. Rugers have a 2 piece bolt that can be sloppy and effect accuracy. This can be fixed by shimming the bolt between usually around .002 and .005 will do the job. If none of this works you might as well just give it away, call me and I will give you my address, LOL!!!
Good luck, Stan