Final answer:
The MK9 Spotting Rifle is a 0.50 caliber firearm used to provide visible tracking of shots to correct the aim for larger weapons. It shoots tracer rounds and is mounted along with the main armament for improved accuracy.
Step-by-step explanation:
The MK9 Spotting Rifle is typically used as an auxiliary weapon that helps in targeting with heavier weapons like recoilless rifles. It is a 0.50 caliber rifle designed to shoot a tracer round with a trajectory close to that of the main weapon, allowing the shooter to see where the much larger projectile will hit and make adjustments. The characteristics of the MK9 Spotting Rifle include its caliber, which is specifically matched to the ballistics of the main armament; its tracer rounds, which enable visible tracking toward the target; and its mounting, which is usually atop the main barrel of the larger weapon for ease of use and accuracy in spotting.