IRL, what looks like tracer bullets bouncing is, in fact, pyrotechnic flare material torn out from the projectile base on impact. This happens even when the projectile in itself penetrates the target. The same phenomenon is clearly visible on many videos showing modern small / medium caliber weapons firing at ground or water (Minigun, Phalanx CIWS, Browning M2, etc.). The trajectory of those pyrotechnic materials shows that what you see bouncing is quite lighter than a bullet.