Actor Grenade : Inventory {
	// Stuff here
}

Actor GrenadeStack : CustomInventory {
	// More stuff here
}

Actor ClipPickup : CustomInventory {
	Inventory.Amount 0
	Inventory.MaxAmount 1
	+Inventory.AutoActivate +Inventory.IgnoreSkill
	States {
	Spawn:
		GREN A -1
		Stop
	Pickup:
		TNT1 A 0 A_JumpIfInventory ("Grenade", 3, "GiveStack")
		TNT1 A 0 A_GiveInventory ("Grenade", 1)
		Stop
	GiveStack:
		TNT1 A 0 A_TakeInventory ("Grenade", 3)
		TNT1 A 0 A_GiveInventory ("TripleGrenade", 1)
		Stop
	Use:
		TNT1 A 0
		Stop
	}
}