The Type 41 light gun received a nominal 80 mm or 8 cm designation during Japan's move to metric terminology. Its origin lay in the British 12-pounder, and its bore apparently remained 76 mm. Whether the gun was bored out is disputed. Continued manufacture of ammunition to the 76 mm standard makes the reboring explanation seem unlikely.
Notable Point · 56:15-57:27
Why an 80 mm Type 41 gun could still have a 76 mm bore
Japan's metric gun names did not necessarily describe a changed bore: the Type 41 example turns on ammunition dimensions and a disputed reboring claim.