We report the experimental data of the fast target protons produced in the reaction of 16O-Em at 3.7A GeV. The emission mechanism of the fast target protons (grey particles with kinetic energy in the range 26 – 400 MeV is studied in terms of multiplicity characteristics. Our experimental data is compared with that of 12C, 22Ne and 28Si projectile interactions at nearly the same incident energy. The results reveal that the multiplicity distribution is independent of both the projectile energy and its size. The interaction events were divided into two categories. The first depends on the number of nucleons remaining as spectators Q (stripped nucleons) from the projectile, while in the second category, the interactions are classified according to the target size (Nh– parameter). The higher moments of the multiplicity distributions were calculated statistically for various groups of events. The experimental data show that the selectivity of Nh particle multiplicity as an indicator for nuclear interaction impact parameter is better as compared to the choice of the charged projectile spectator nucleons Q in each event.