=D
maybe it only vomits the bullets that are shot at it and only energy weapons can kill it.
the more bullets sunk into it the more powerfull the attack can become... maybe idk 1/8 of the damage of the bullet sunk into him.
and some sort of... time/power control like when using the luci , and to have the effect of it blowing up... idk maybe he can choke on the bullets?