Although the captured HK417 was a good rifle, Gao Yang was still not very comfortable using it. The reason was simple; he had only fired a few rounds with the HK417's ammunition and didn't have the time or means to perform long-range ballistics testing. Gao Yang could guarantee the accuracy of his M14EBR at a distance of 800 meters, but with the HK417, he had no confidence at all.
Gao Yang had never expected that one day he would really need to use the HK417 as a backup gun, so despite having the gun in his hands for quite some time, he had never made a specific effort to familiarize himself with it.
If Gao Yang had been given a few more days to get accustomed to it, he could have fully leveraged the power of the HK417. But at present, he only dared to ensure accuracy within 600 meters; beyond that distance, the variation in the bullet trajectory was too great for him to be confident of hitting the target.