Sort of.Most of the m/28-30 versions were derived from target rifles, and had .308 diameter bores. That allowed them to utilize the Swiss boattail/Spitzer bullets developed for the 7.5 Swiss M1911 rifles and used around 1927-'28 in American match loadings for the .30-06 Springfield. The M39s had a bore of closer to .310-.312 [I've slugged the bores of the 5 M39s I've had, and they vary] and had deeper chambers cut to allow the use of both Finnish Finnish D-166 200-grain ammunition and captured Russian ammunition with .311-.312 diameter bullets; accordingly their chambers were marked with a *D* stamping- as were many former Civil Guard M28 and M28-30 rifles. Whether that's an *improvement* or not is debatable; obviously it was of certain military advantage at the time, but boy oh boy, does my M28-30 like the 168-grain Sierra match King bullets....
BTW: The *D* stamp is sometimes located on the rear sight base...
