There is a Lyman front sight and what appears for be a "target sight" (probably also a Lyman) on the rear of that rfle, so I will guess that it has been "sporterized". From your photos it appears to be a (originally) 6.5 x 50 Japanese Type 38, but from the photos the bore is neither a 7.7 nor a 6.5. I am guessing it has a .308 (.30 caliber) bore.
Are there any other stampings on the rifle to indicate another caliber that it may have been converted to? If not, I once again strongly urge you to have a competent gunsmith gauge/slug the barrel to confirm the bore and cast the chamber to confirm the cartridge dimensions.
Other than to tell you that neither the 7.7 or 6.5 Japansese cartridges appear to be correct for your rifle, no one will be able to tell you what to do until you get the gunsmith's inspection done.
Later edit: From the photo of how the barrel fits flush up to the receiver, it looks like a complete re-barrel to me.