I've only owned one Model 760 and it was not in .308. It was, however a nicely made and accurate rifle. As far as effective ranges for the rifle and chambering, I'd answer that to be whatever range the rifle and shooter remain effective enough and not to exceed somewhere around 500-600 yards (allowing a full 1,000 FPE there).
At this long range, a rifle would need to shoot no more than MOA (about 1", or less group at 100 yards) and allow the shooter to hit a 6-8" circle consistently at that range. Using a bullet with high B.C. and velocity of around 2700 FPS (+/-) you would still carry 1,000 FPE out there. However, trajectory becomes problematic. Using a sight-in with the bullet striking about 2.5" above POA at 100 yards, the bullet would be some 4 feet low at 500 yards. As you can see, not a typical shot.
A more effective way to figure the max effective range might be to simply figure max point blank range, (MPBR) with the bullet never being more than 3" high nor 3" low within a given distance. The .308 shooting a good 165gr hunting bullet (B.C. of .475) sighted like that will give you a MPBR of about 270 yards, allowing you to shoot from muzzle to 270 yards without a correction needed in your aiming. For most practical hunting applications, this is a very good way to sight in such a rifle & cartridge combo. For reference, having the center of your groups hitting about 2.5" above POA at 100 yards will do this for you.
Last edited by turner; 07-21-2011 at 12:57 PM.