RP General Discussion

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from the wiki

Barrett

Originally posted by wiki

Muzzle velocity
853 m/s (2,799 ft/s)

Effective range
1,800 m (1,969 yd)

Coilgun

Originally posted by wiki

Adjustable yet smooth acceleration of the projectile throughout the barrel can allow somewhat higher velocity, with a predicted range increase of 30% for a 120mm EM mortar over the conventional version of similar length. With no separate propellant charges to load, the researchers envision the firing rate to approximately double.[14][15]

Speed of sound
343.2 m/s

Initial margin:
the bullet from the muzzle is traveling
853 m/s = 1908.10666 miles / hour = 2798.55643 feet / second
which means
853-343=510m/s faster than sound

510 m/s = 1140.83751 miles / hour or 1673.22835 feet / second faster than sound.

the bullet of just the barrett can travel about 9.3 football fields in a second
the effective range is 1800 m, about 18 football fields, therefore it takes 2.1 seconds to reach a target.

in 2.1 seconds, the sound wave of the gun firing would be 2.1 seconds * (343 meters / second) = 720.3 meters away from the source, 1079.7 meters away from the target.

now the only thing left would be...
the "bubble" around the bullet, which I doubt would give anyone enough preliminary warning to dodge it cause you have to take reaction time and the speed in which your body moves and how far it would take to move out of the way and thus the reaction time + the time it would take to move out of the way.

Then there's muzzle flash...