The specified maximum diameter of an unfired .50 BMG bullet is 0.510-inch (
13.0 mm); while this appears to be over the .50 inch (
12.7 mm) maximum allowed for non-sporting Title I firearms under the U.S. National Firearms Act, the barrel of a .50 BMG rifle is only .50 inch (
12.7 mm) across the rifling lands and slightly ...
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