Groove diameter, DWM specs:
min: 0.3098
nom: 0.3110
Max: 0.3114
This is a tighter spec than most US made barrels. The idea that Luger barrels vary in diameter is another one of those urban myths. That said, there are a few around that have been rebarreled with US 308 barrel stock.
Chamber mouth diameter:
min: 0.3331
nom: 0.3339
max: 0.3346
I include the chamber mouth diameter because it is important to make shure the cartridge outside neck diameter is at least 0.001 smaller then the chamber neck diameter. You must leave room for the neck to expand or pressures will rise.
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