As far as different rounds go...
The time in flight on the *recording* is still the same.
Shooter1=0.559s, Shooter2=0.374s (time from impact to report)
Different rounds *would* make a difference in the distance they are away from the *source of the recording* - but not that much.
M193 5.56x45mm 55gr 3250fps: Shooter1=400yds, Shooter2=250yds
M855 5.56x45mm 62gr 3025fps: Shooter1=400yds, Shooter2=250yds
M80 7.62x51mm 149gr 2750fps: Shooter1=410yds, Shooter2=270yds
M2 7.62x51mm 152gr 2740fps: Shooter1=420yds, Shooter2=270yds
M852 7.62x51mm 168gr 2550fps: Shooter1=450yds, Shooter2=290yds
M118 7.62x51mm 173gr 2640fps: Shooter1=420yds, Shooter2=270yds
Mix and match at your leisure.
And it is my understanding that the samples were taken from the same video within seconds of each other. Which means very little time for a single shooter to either switch rooms, switch rifles, or reload.
And the approximate location of the recording device can be estimated using google maps.
Different rounds *would* make a difference in the distance they are away from the *source of the recording* - but not that much.
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Take a look at 7.62X39.