US Mach 7.3 'Bullets': The U.S. Navy Tested a "Hypervelocity Cannon Round"

Cheap!

Works in existing barrels.

"The HVP is a next-generation, common, low-drag, guided projectile capable of executing multiple missions for a number of gun systems, such as the Navy five-inch; Navy, Marine Corps and Army 155-mm systems and future electromagnetic railguns," BAE Systems, which builds the hypervelocity shell, explains on its website.

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