I could swear I have something around here, and I'll be darned if I can remember what it is or where it is, that indicates that the nominal base diameter of 7.7 military rifle ammo to be closer to .480 than .470...
I know the .311 bullet isn't an issue. if anything, that will raise pressure a few thousand PSI, if any at all, from the nominal working pressure of the cartridge, and IIRC the nominal working pressure for the 7.7 is 54,000 PSI, while for the .30-06 its closer to 65,000 psi, so there's a lot of inherent leeway.
Oh, by the way, I've seen several Arisakas over the years that would chamber the 7.7 semi-rimmed ammo out of the feed strips. Don't ask me why or how.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.