All arrows are supposed to deal more damage based on speed, even ones from dispensers.

From the wiki:"Arrows fired from dispensers always do 3 (1.5 hearts) damage unless their velocity is modified by an external source"

But in bedrock 1.19 and above, it doesnt seem to be the case.

Steps to reproduce:

1. Load the structure file provided using a structure block (make sure the front of the gun faces an open space)
2. Place a few iron golems in front of the gun
3. Press the button to fire the gun

Expected result: The Golems get killed instantly (as the arrows are going fast enough to do that)

Observed result: Barely any damage is dealt

This also affects all 1.19 versions in bedrock on all bedrock platforms. It doesnt exist in 1.18 bedrock or java

1.18 bedrock: https://youtu.be/7ajz5-ocCrM?t=59
Java: https://youtu.be/YQLiXXncdKk?t=35 

Update: I managed to get an accurate velocity measurement of the arrows which is 1500 blocks/s or 75 blocks/game tick for this railgun. The arrows should deal 150 dmg using the 2 damage/(block/game tick) damage value for normal arrows. (vid of me measuring the speed is attached, i played the vid frame by frame when the cannon fired)

Update 31/7/23 : Bug still affects 1.20.12 and other 1.20 versions. Also tested in 1.18.0, with normal and harming arrows, and only the harming arrows killed the golems proving GoldenHelmet's hypothesis correct.