On my 308 gas gun I tried 8 different powders before I found the one. It would do 1 inch to 1.5 to even 4 inches with 1 brand of bullets. With AR comp and 165-168 grain bullets it's an honest .4-.5 gun.
I'm not sure if you reload. ***Use at your own risk. If you do try 41.5 of imr 4895 in LC brass, 39 grains of 3031, 42.8 of imr 4064 *** Gold Medal Match Clone, 46 grains of Varget ***this is a max load, work up to it. 40.6 of AR Comp in LC Brass, 41.7 AR comp in REM Brass, 42 AR Comp in Win. Brass. All of these loads use 165-168 grain bullets. I use Fed 210 primers but CCI 200s will work. These are known accuracy loads in the 308. Some are old military match loads. Unless specified I'm using commercial Winchester brass. Work up to these loads carefully. Very carefully.
If your rifle won't shoot one of these loads decently you very likely have a gun or a scope problem. Also check your scope mounting system as well as parallax.