The US Navy is quietly pushing ahead with a radical new cannon that one day could transform how wars are fought, even though some Pentagon officials have voiced concerns over its cost and viability. Named the railgun, the weapon in question represents a paradigm shift in ballistic technology. Instead of using gunpowder and explosive charges to shoot a shell from its barrel, it employs vast amounts of electromagnetic energy to zoom a projectile along a set of copper-alloy rails.

Scientists expect the railgun rounds to travel at speeds up to Mach 7.5, which at 5,700 mph (9,100 kph) is more than seven times the speed of sound, and cover a distance of about 100 miles (160 kilometers.) The futuristic weapon has long been a darling of the Navy’s research wing, along with other game-changing technologies such as laser beams that can track a boat in choppy water and blast holes in its hull.

Yet the railgun, which so far has cost more than $500 million, may find itself becoming something of a victim of its own success — even before it is made operational. That’s because of its special shells designed to hurtle through the skies at jaw-dropping speeds. These rounds, called High Velocity Projectiles (HVP), can be guided in flight. They can also be fired from a conventional five-inch cannon.

Though the HVPs would travel slower than they would out of a railgun, they still outperform regular shells, making them a tempting proposition for the Navy to deploy across its fleet.

The Navy hopes to install a railgun on the USS Zumwalt, a brand new guided-missile destroyer that produces the large amounts of power needed to charge the weapon.