The very early (dog leg flat bolt) tang safety M77's had Douglas barrels, as production increased Wilson barrels were used until the transition to Ruger hammer forged barrels took place. Some very late M77's have the hammer forged barrels, and I am pretty sure that all MKII's do. Yes, the 7mm barrels have a fast twist as do the 6.5 barrels. I can't remember for sure, but I think that the Wilson barrels had six grooves, and the Ruger barrels have 4........ I could be wrong about that.