So recently I was doing research on Magnetic Coil based weaponry in the Halo universe, and while reading about how the "Super Mac" worked, I noticed that the theoretical speeds at which the Tungsten Steel slugs weighing around 3,000 ton were being fired, which is about 12,000 km/s or 4% the speed of light, could be repurposed to fire spacecraft at faster speeds than many conventional forms of travel in space. Let me also clarify, I understand that within the Halo universe there are Translight space drives, but I mean this to be theorized in the present to near future, not millennia away. I would like to know the communities thoughts on this form of space travel. (Sorry if my question is confusing, I'm not a professional writer :D)
CLARIFICATION & INFORMATION
So to clarify exactly what a "Super Mac" is, it is a Magnetic Acceleration Cannon. The science behind how it works is a little more complicated than I can admit is understand, but the best way that I can describe it in my word is that it is a long metal cylinder wrapped in a coil made of magnetized metal that when given a current creates a magnetic field that when an object of the opposite magnetism is placed in the field, it suspends the object in an almost Zero Gravity environment which creates a frictionless environment opposite to how a gun works by firing a bullet through a cylinder that has friction.