7.7x58 will not chamber?

[WNO1958]

Did you load the round in the magazine and then close the bolt? The Type 99 has a mauser type extractor. This means you can not just drop a round in the chamber because the extractor cannot snap around the cartridge rim. The cartridges need to be loaded from the magazine.

If it does not work by loading from the magazine, suspect that the barrel has been converted to a new caliber.

I apologize if this response seems too basic, but I don't know your level of expertise.

Walter