The feat can be found here
Object = 2atan(Object_Size/Panel_Height/(tan(70/2))) = 12.44 degrees
Panel heigth = 480 px
Sam's head = 75 px = 25 cm
Using this calculator the distance is 1.1469 meters.
Sam's hand and the colt should be at least 70 cm long so the distance between the bullet and Astaroth should be at most 0.4469 m.
The muzzle speed of the Colt is 270 m/s according to this wikipedia page.
V = x/t
t = x/V
t = 0.4469/270
t = 0.00165 seconds (1.65 milliseconds) which is supersonic perception according to this page
Astaroth's hand moved at least 0.5 m so it's speed is v = 0.5/0.00165
V = 303 m/s (mach 0.89) Subsonic+
So Astaroth has Subsonic+ movement speed with Supersonic reaction time