The U.S. military gives the velocity of the lead-free M80A1 round as 3050 fps at 78 feet (26 yards). This velocity is most likely stated based on a 22-inch test barrel. The velocity would be reduced by about 25 fps per inch for shorter barrels. This article compares velocities from a 16″ barrel. The 6-inch shorter barrel reduces velocity by 150 fps to 2900 fps at 78 feet. At the muzzle, this works out to 2970 fps. (In the JBM ballistics program, I’ll enter 2900 and 78 feet as the values. For the ICS rounds, I’ll use the calculated muzzle velocity and 1 ft for location of chronograph.) The drops are calculated with a 200 meter zero.
The G7 BC of the M80A1 was estimated based on the discussion in this post: What is the G7 BC of the M80A1? The BCs of the ICS bullets are Litz G7s.
Each of the three ICS rounds has better values at 900 meters for drop, drift, velocity, energy, and time of flight, with the sole exception of drop for the 142 grain ICS round. The best round for drop and time of flight was the 107-grain ICS. But the 142-grain ICS had the best values for drift, velocity, and energy, all at 900 meters. The 123-grain round might be the best compromise between those two options, with the second best out of all four choices for all criteria: drop, drift, velocity, energy, and time.
At 500 meters, the story changes. The M80A1 has the best values for drop and time of flight, due to its high muzzle velocity, despite a poor BC. For drift and energy, the 142-grain ICS round excels, due to its high BC and high weight. Then the 107-grain ICS has the best value for velocity at 500 meters, due to the combination of a good BC and moderately high muzzle velocity. The 123-grain ICS again makes a good compromise, having pretty good values for all of the criteria.
Velocities for the ICS rounds, with a 16-inch barrel:
107-grain at 2750 fps
123-grain at 2590 fps
142-grain at 2400 fps