The 55 grain M-193 and 62 grain M-855 ammo work fine in the 1 in 7 twist as well. But,, those projectiles start loosing out past 400 meters compared to the longer and heavier slugs. I shot some pop-ups at 700 meters ( machine gun range), with M-193 ammo and about 30% of them were keyholing. The M-855 green tip did much better with only a few showing some yawing. I fired both from a 1 in 7 twist weapon.
The 1 in 7 twist was not needed for the 62 grain green tip ammo, but rather for the longer new tracer rounds.
The 77 grain match slugs really shine in the 1 in 7 twist.