Lavid2002
I think one way to tell the Type 38 6.5mm receiver apart from the later Type 99 7.7mm receiver is to look at the gas ports near the receiver ring. Type 38 rifles had two gas ports; the Type 99 had only one. There are other differences, such as the Type 99 had a longer, one piece tang to give more support to the grip section; also the tang sections, trigger guard, and magazine floorplate were all made from stampings. Basically the Type 99 (1939) was an attempt to modify the older Type 38 (1905) action so as to make it easier and quicker to manufacture. And at the same time, they decided to chamber it for the newer 7.7mm cartridge. The most common Type 99 variant was the Short rifle which was 44 1/4" long overall, and weighed around 8.5 pounds.