I was sure about the semi-rimmed after researching these, problem is not all sellers list the semi-rimmed as such so you have to be careful before ordering some of the surplus. Actually I asked CL at LibertyTreeCollectors and he told me roughly the same thing but wasn't 100% sure. I'd pretty much come to the conclusion that they (Arisaka and Jap) were the same but didn't want to tell my buddy it was ok to use until I knew for sure. Rifles with intact chrysanthemum's or as we call them, mum's for short are the best examples you can get, though rifles with ground mum's are okay also, just different history. The chrysanthemum's were ground off when the Japanese surrendered their rifles at the end of the war as the Chrysanthemum Empire was no more, GI's were also required to deface captured trophy rifles as well at wars end. The marking your looking at on the receiver is a chrysanthemum flower denoting, or the symbol for the Japanese, or as they termed it the Chrysanthemum Empire. Use the regular 7.7 rimless ammo in your Type 99 that is the correct ammunition.
The Japanese ammo is referred too by both names 7.7 Arisaka and more commonly 7.7 Jap, your correct the Japanese also had a 7.7 rimmed round for machine gun use, the Japanese even produced a machine gun similar too the British Bren machine gun, both used rimmed ammo, one reason for rimmed machine gun ammo, widespread use in the Jap type 99 machine gun.
Are these the same rounds as long as they aren't semi-rimmed which is also called by the same names sometimes? The other thing I found is the 7.7 is called 7.7 Arisaka and 7.7 Jap. First thing is I found there's a semi-rimmed cartridge that won't/shouldn't chamber in these because the machinegun 7.7 round is way to hot for the bolt gun and that's why they put the rim on it. He asked me to find some ammo for it and when I looked I found there's different stuff available. My nieghbor says his dad has one he brought back from the war and has been hanging on the wall every since. I have a question about the ammo for these. It was a long time ago but it had the same insignia I believe, the rising sun. What I mean by partially restored is actually I gave it a real good cleaning and made it functional again. It was a friend of mine's gun that had been neglected. I believe I've partially restored one of these about 22 years ago. The wood, well looks like the Japanese were cutting some nice trees down towards the end, interesting note the seller advertised it as a Jap trainer, when I saw it I knew exactly what is was and had to have it despite the poor condition upon delivery. I really like to feel the metal getting warm and see a little smoke whisping out of the action on an old rifle that has not been fired in decades, really nice to wonder, perhaps in this instance, If I may be the only person to fire it and see smoke from the end of the barrel since it was surrendered and entered the states, I'm just sentimental like that. One thing I love as much as owning these old pieces of history is owning a functioning piece of history.
To answer your question Dolk, I have shot it and even with the fixed peep site at hundred yards it shoots straight, at least it will blow apart a clay on the side of a pumice quarry. One that has eluded me for over a year now. Dolk wrote:Stripes on an Arasaka?.I'll take it!