entity damage cooldown (red pain state) problem

I am trying to make a gun mod and i have a shotgun which shoot multiple projectiles at once, the problem is if i try and shoot at a single entity, only one projectile would hit, i think this is because of the Minecraft 'pain state' mechanic, which makes entities turn red and ignore most types of damage for the next ticks afterwards.

How can i fix this? Any way to bypass this 'damage cooldown' mechanic so all projectiles hit? Same problem with automatic fast shooting guns.