MC-94978Throwable items fired from dispenser do not hit mobs for the first two ticks
Dispensers can fire snowballs but they don't hit mobs (hostile and passive).
It is the same problem with eggs, but all is good with arrows.
Code analysis by Marcono1234 in this comment
[Mojang] Jeb (Jens Bergensten)
2015-12-30, 01:41 PM
2016-09-18, 06:33 AM
2016-08-09, 04:43 PM
20
10
Minecraft 15w50a, Minecraft 15w51a, Minecraft 15w51b, Minecraft 1.9