If you want to try shooting further I would make one suggestion...Do it!1/2 MOA is promising for further testing for long range accuracy. I would always recomend handloading as this, along with trigger tunning are often the biggest improvments for the least amount of money. Some of my 308 pet loads are 42gr Varget behind 175 SMK (I usually use Lapua brass, and remington 9 1/2 primers), 42.8gr 4064 with 168gr A-max, 45gr Varget with 155gr Lapua Scenar (*this is a max load), I also like the Berger 185 VLD (try it with 42+gr of 4064). When testing these or other loads in your rife always start low and work up. All of these loads are capable of consistantly shooting eggs at 500yds, and busting clay pigeons over 700yds. I have no experience with rugers, but that rifle sounds like it has some long range potential especially if you can develop some accurate handloads for it. Have fun. Here's a link to a thread discussing 308 bullets
bullets for 308 win