We picked this up earlier this week. It is just like our other one in 7.7 Jap and the 7.7 ammo fit in there and cycled so we went out to shoot it and the first shot freezed up the bolt. We ejected the non-fired cases from the magazine and tried getting the bolt open. We couldn't so we went home and today I pounded the bolt open and this is what I found. The case had just fine pressure, the primer and head are not deformed, but it's the case neck that's expanded. We compared the bolts with our other one and they're the same length and dimensions. So I started thinking, if it's a original military bore (which it is), the bolt is the same, but the case had expanded by the neck than whatever the correct caliber is , it's a longer case than the 7.7 Jap. All I know is the Arisaka's came in two calibers, 7.7 and a 6mm version. Is there a third caliber that I do not know about? The different caliber chambering got me thinking so I grabbed a .308 case to compare and I discovered that the rims of the 7.7 and .308 are identical and fit in the bolt. The .308 is shorter than the 7.7 but a 30.06 would be longer than them both. So I think this rifle had been converted to 30.06 but I can't confirm it because I do not have 30.06 ammunition in the house. Here are pictures so any of you can help me discover what the problem is. 1st Pic: The rifle itself 2nd pic: the expanded fired case 3rd pic: 7.7 Jap, our expanded case and a .308 4th pic: A .308 fits perfectly in the bolt.