A modular bullet trap cover element generally includes a shell filled with a projectile trapping medium, preferably a mixture of a resilient granular ballistic medium and a hydrated super absorbent polymer (SAP) gel. The shell may be made of any of a number of fabric or polymeric materials. In embodiments, the shell includes at least two bags, an inner bag and at least one outer bag, each of which has an open end and a sealed end, connected to one another such that the outer bags may be inverted over the inner bag to cover at least a portion thereof. The modular cover element is formed by filling the inner bag with the projectile trapping medium and then inverting the outer bags to produce a multi-layer shell. In embodiments, the outer bags and inner bag are rotatably connected, permitting the outer bags to be rotated with respect to the inner bag such that bullet holes in the inner and outer bags no longer line up with each other. Several modular cover elements may be fixedly or releasably interconnected, preferably in a mattress-like arrangement, to form a bullet trap cover.