Many 7.7 Jap rifles had their barrels set back and re-chambered for .308 brass and .312 bullets to ease finding suitable components. Thailand after WW2 had captured Arisakas done up in 30-06,the NVA in 7.62x39 and a batch of 7x57 for Mexico [which they neglected to pay for] so didn't receive the second shipment.Many 38's done up in .257 Bob or a 6.5 version of the above retaining the original barrel.......Harold