They do have 5% of the speed of light projectiles which are just as deadly. The delivered energy will do more than enough damage to render the tank inoperable.
And really, not meaning to be disrespectful, but they that is kind of a Luddite remark. Something I use to hear when they were discussing Reagan’s star wars programs.
5% of C is 9300 miles per SECOND. What are you smoking?
The actual Luddites attacked textile machinery, for fear it was rendering their jobs obsolete. So, as the story goes, they had disdain for new technology. But...it was actual, functioning, not pie in the sky but really working, technology.
Stating that something that has never been demonstrated, such as a man portable rail gun capable of launching projectiles tens of thousands of feet per second, does not make one a Luddite. Using that logic, if you don't believe I can make my decade old Hyundai win at the drag strip, using a special racing chip, you're a Luddite.