From an outdated version of the Blue Book of Gun Values (26th Ed.)
pg.370 the B-78 came in 22.250,6mmRem. ,.243 Rem. , 25-06, 7mmRem. ,30-06, or 45-70 round or oct. barrel 24or 26 inch barrels, no sights save for the 45-70.
Approx 24000 made between 1973 -82.
So yes, they chambered it in a .30 Cal.
Tight Groups, Happy Searching,
Rob