At the normal speeds at which planets, ships, and other bodies travel through space, Newtonian laws of physics are observable. For example, the Doppler Effect can be observed even on Earth. At these speeds, the laws of Relativity are not observable.
At the high speeds at which the Bobs and their weapons travel, the effects of Relativity become significant. For example, time dilation associated with the Lorentz factor becomes more apparent.
Often, one of the Bobs will describe a weapon (such as a cannonball fired from a rail gun) hitting a target at "near relativistic speed." This means that the object was traveling so fast that the laws of relativity were starting to be observable, from the object's perspective.