Except for some minor differences in dimensions, the main difference between the Mk 3 projectile and the Mks 1 and 2 is that there is no hole in the base of the Mk 3 for a tracer or plug. This design was developed when the tactical need for non-trace ammuni-tion arose; but with the appearance of "Dark" tracers, the Mk 3 projectile's original pur-pose was eliminated.

Figure 76. 40-mm Projectiles.