I have had several rifles with pitted bores, that was the way it was with many surplus rifles 25 years ago, not like now with all these arsenal rebuild guns so common, were getting spoiled with em'.
My Italian Carcano in 6.5 had pitting, Japanase Arisaka in 6.5, pitted, my Spanish Mauser in 8 MM, pitted, my British Enfield, #4, pitted, in fact all these mentioned rifles were some of the most accurate I ever had.
I bought a 1943 Tula MN 91/30 last year that had deep pits in the groves, but boy it could shoot. Traded it off as my other 2 Mosins have minty bores and also shoot well.