The often heard claim that a 1:12 twist in a .308 Win. barrel will not shoot heavy bullets accurate is well countered with facts in the link below:
Note the M1 and M14 arsenal match barrels used at the time had 1:12 twists. Lapua 185-gr. FMJRB bullets were used in USN and USAF M1's rebarreled with 1:12 twist 7.62 NATO chambered ones and shot sub MOA at 1000 like the 190 Sierra's did. I've shot hundreds (thousands?) of each in Garands and can well attest to the accuracy they produce.
My bottom line is, a 1:12 twist will shoot 155's through 190's the most accurate. But unless you've got at least 29 inches of barrel, the 155's won't leave fast enough with safe pressures to remain supersonic through 1000 yards.