Improves bullet projectile embedding handling

Commit b1546ee3eb contained a rather
bone-headed mistake, that resulted in embedding with penetrating
projectiles to not behave as desired.

This commit fixes that, and provides a cleaner implementation.

code/modules/projectiles/projectile/bullets.dm

@@ -7,23 +7,37 @@
 	check_armour = "bullet"
 	embed = 1
 	sharp = 1
+	var/mob_passthrough_check = 0
 
 /obj/item/projectile/bullet/on_hit(var/atom/target, var/blocked = 0)
 	if (..(target, blocked))
 		var/mob/living/L = target
 		shake_camera(L, 3, 2)
 
+/obj/item/projectile/bullet/attack_mob(var/mob/living/target_mob, var/distance, var/miss_modifier)
+	if(penetrating > 0 && damage > 20 && prob(damage))
+		mob_passthrough_check = 1
+	else
+		mob_passthrough_check = 0
+	..()
+
+/obj/item/projectile/bullet/can_embed()
+	//prevent embedding if the projectile is passing through the mob
+	if(mob_passthrough_check)
+		return 0
+	return ..()
+
 /obj/item/projectile/bullet/check_penetrate(var/atom/A)
-	if(!A || !A.density) return 1 //if whatever it was got destroyed when we hit it, then I guess we can just keep going
+	if(!A || !A.density) return 1 //if whatever it was got destroyed when we hit it, then I guess we can just keep going
 
 	if(istype(A, /obj/mecha))
 		return 1 //mecha have their own penetration handling
 
 	if(ismob(A))
+		if (!mob_passthrough_check)
+			return 0
 		if(iscarbon(A))
-			//squishy mobs absorb KE
-			if(can_embed()) return 0
-			damage *= 0.7
+			damage *= 0.7 //squishy mobs absorb KE
 		return 1
 
 	var/chance = 0