Since the video quality is really bad, I would explain it here.
First, I used P2020 and wingman to shoot from 45 metres. P2020 lost its headshot bonus while wingman does not.
Then, I used R-301 to shoot from 44 metres. It did not lose its headshot bonus.
Third, I used Splitfire to shoot from 56 metres, it did not lose its headshot bonus.
Then I used L-Star to shoot from 62 metres and it lost its headshot bonus.
Prowler also lost its headshot bonus from 42 metres.
Splitfire lost its headshot bonus from 72 metres, while wingman did not.
Alternator lost its headshot bonus from 42 metres.
At last, PK did not lose its bonus from ~52 metres.
It is a little bit messy to read.