7.62x51mm NATO dummy round

This is a 7.62x51 dummy round. The difference between 308 win and 7.62x51 is pressure and a few dimensions that are a thousandth of an inch different. A rifle chambered in 308 can shoot both 308 and 7.62x51 because 308 has higher pressure than the 7.62. The 7.62x51 rifle can but it is not recommended to try firing a 308.
I suggest printing the model oriented to rest of its rim.

There is a dimensionally accurate file and a loose file for FDM printing.