First...does adding Replicating a magic item to your artificer mean you automatically create it or do you have to have one to replicate?

Second...what about replicating Walloping ammunition...do you only replicate one? Or can you replicate more than one? Because of this vs a non consumable, I am very confused about this feature...thank you!  

Hi there. When you take Replicate Item, you do not need an original to copy. For Artificers, it’s not so much that they “copy” something, it’s more that they figure out some magimechanical way to “replicate” a magic item.

If you take Walloping Ammo, you can only make one at a time, but you can make a new one every day.

Can an Artificer of 14th level or higher replicate very rare items? Specifically an Amulet of the Planes?

The replicate magic item feature allows you to "replicate a particular magic item... from the Replicable Items tables".

Amulet of the Planes isn't on the list I'm afraid.

thank you for your reply. The text is a little ambivalent.

Replicate Magic Item

Using this infusion, you replicate a particular magic item. You can learn this infusion multiple times; each time you do so, choose a magic item that you can make with it, picking from the Replicable Items tables. A table’s title tells you the level you must be in the class to choose an item from the table. Alternatively, you can choose the magic item from among the common magic items in the game, not including potions or scrolls.

The bold is mine. Items that are on the table do include wondrous rare items but not very rare. So from reading the text you could replicate a wondrous rare item that is not on the list. 

My question is could you replicate a wondrous very rare item. Specifically an Amulet of the Planes. I read "common magic items in the game" to mean anything that was in the Dungeon Master's Guide. I could be wrong and that is why I asked the question.

All of the items on the list that are wondrous are rare items. But a 14-20th level artificer might be powerful enough to create a wondrous very rare item including an Amulet of the Planes. IMO I don't think it would be overpowered because many magic wielders that have access to 7th level spells can cast a plane shift spell.

No, you cannot replicate any Very Rare items, or any Uncommon or Rare items that are not on the list. The only items you can replicate that are not on the list must be of Common rarity:

Replicate Magic Item

Using this infusion, you replicate a particular magic item. You can learn this infusion multiple times; each time you do so, choose a magic item that you can make with it, picking from the Replicable Items tables. A table’s title tells you the level you must be in the class to choose an item from the table. Alternatively, you can choose the magic item from among the common magic items in the game, not including potions or scrolls.

Thank you IamSposta.

You are right. Wow, my headspace was way off. Thanks again.