Type 99 "Basement Find"...

[vintage hunter]

I have heard the Arisaka 7.7 can fire the British 303 cartridge but not the other way around the Japanese cartridge case being longer so would not chamber in the Lee Enfield from what I also recall the 7.7 round is semi rimmed

Don't waste your time looking 728, there is no way a 303 round could possibly be fired in a T99 as is. It would be possible to convert the 303 cases if there was no other option I suppose by reducing rim thickness/ diameter, cutting an extractor groove and fire forming but it's much simpler to reform 30-06 or 270 cases. I've even necked down 8x57mm cases. There were/are 3 types of 7.7x58 ammunition, rimmed, semi-rimmed and rimless. All rifle ammo was rimless, the other types were for MG's.