Having followed this stuff for quite some time, my take is a good barrel is a good barrel regardless of groves, ratchet, squares or rectangles.

And two groves are some and some. If done to spec, they performed on par with 4 and 6 (Smith Corona produced a fair number of barrels in 6 grove late into the war) )

Done wrong, the two groves of course did not shoot well.

It was an expediency measure, the bolt actions were usually second tier use not front line (some did serve and beyond snipers) but most were rear line troops, artillery, chemical, prisoner of war, Seabeas (those two used Model of 1917s) just anyone that needed a weapons but not a Garand.

Oddly one mfg said it was going to9 reduce their rate to go from 4 to 2 and kept on making them as 4s under an exemption (they were setup and two is a lot different than 4)

Range had nothing to do with accuracy, either they were or were not. Groves do not either.