Full Auto

The Fine Balance series is unlocked after completing the Tough Guys series. There are eight races to complete, and all involve B-class vehicles with your choice between a standard forward-mounted machine gun and rear-firing mine layer, or forward-mounted shotgun with rear-firing grenade launcher.

You need to meet the Survivor requirements for all eight races to earn this Achievement. Pay attention to the individual race requirements and try for the Gold while you're at it, since there's an Achievement to earn for getting a Gold (Full Auto) medal on all races.

Once you pass the requirements for all eight races, the Achievement will unlock.

I recommend using the shotgun/grenade loadout. The shotgun does more damage on a single hit, and can be aimed using the Right Analog Stick so you can stay out of the line of fire from your opponents' rear-firing weapons. When dropping grenades, either wait for an opponent to get right behind you so that you can hit him with all four, or drift from one side of the track to the other so that you lay a strip right across the road that is harder to avoid.