Re: 308 on deer to 600yds
CapDog hit the nail on the head for the SMK at 308 velocities.
Depending on the velocities youre getting the 168, 178 AMAX bullets are decent 600 yard deer loads as is the 150 ACCUBOND. If it were me and I was going to draw the line at 600 or 650 for that matter, I would look long and hard at the 150 ACCUBOND. It will hit with just over the published minimum expansion requirements out to 650 yards even starting out at 2800 FPS. At 600 it will deliver just short of 1000 pounds of energy. With your LTR, you may be limited to about 2800 FPS. The terminal performance of the 150 AB on several critters from 318 yards out to 600 yards has been excellent.
Another magic 600 yard 308 load is the 200 Sierra game king. Loaded to 2400 FPS it will hit at 600 yards with 200 FPS more than needed to open the bullet and deliver more than 1100 pounds of energy.
My personal 2 top picks are the 200 SGK and the 150 Nosler AB with the 168 or 178 AMAX being a good second choice.