I have a Model 1900 which is typical of all the M-S Steyr of that era, double-set triggers, claw scope mounts, butter knife bolt handle. From information found here and other locations I read that the model 1900 was in 6.5x54M-S. This one was purchased as an 8x56 M-S and appears to be. Having a bit of an issue with ammo though. Bullet diameter listed for these suggests .323 as correct and that is what I was trying. First attempts had several that would not fire. I suspected the shoulder was not supporting the case so I made a new batch of cases by necking up 8x57 Mauser cases to .358 and then using a full length sizer for 8x56 to form a new shoulder. I backed the die off a couple of turns and started sizing and trying the case in the chamber until I got a good fit with the bolt just closing. I shot several of these and although my elevation was off with the fixed and folding rear sight I was generally pleased. I wanted to make a few more cases last night and decided I would use a .338 expander instead of .358. When I went to form the shoulder all of the cases would chamber, no matter how much I backed the die out. So I thought my chamber is a little large. Then for some reason I picked up a .308 bullet on my bench and stuck it nose first into the end of the barrel. I surprised me when it stopped and would not enter completely. I then tried it in 2 8x57 Mauser rifles and the same bullet dropped all the way through the barrel. All this makes me have questions. Does my rifle have a bore made for the .318 diameter bullet? If so, why is my chamber so big? I will try to case a suitable slug to push down the barrel to try and get a correct bore diameter.