In that first frame shown here, the bullet has not yet left the barrel, however in the very next frame after, a beginning puff of smoke is the giveaway, that the bullet is on the way.



The next frame reveals the smoke puff growing larger, but the bullet has not yet arrived at the jug.



In the following frame the bullet has just arrived at the jug, and the smoke from the rifle continues to spread.



Several frame later the jug is long gone; the smoke plume grows, and water drops fly across the front of the camera.



In order to learn the time it takes for the bullet to get from the rifle to jug; one just counts frames between the second picture shown above and the first frame one comes to, that shows the bullet impacting.

the way i do math that is a heck of a poke.
14-15 frames = approx. .5 seconds
1880 fps = 940 ft.

The bullet starts to slow down the instant it leaves the muzzle; your calculation doesn't take this into account.

Frame count is real close; could be improved.