Thrown Arms Master and Returning Weapon Infusion

Question

Thrown Arm Master is an interesting feat from the Tal'Dorei Campaign Setting Reborn, but I'm curious about its interaction with the Returning Weapon infusion. Namely the following part about Thrown Arm Master:

Simple and martial melee weapons without the thrown property have the thrown property for you. One-handed weapons have a normal range of 20 feet and a long range of 60 feet, while two-handed weapons have a normal range of 15 feet and a long range of 30 feet.

How does this interact with the returning weapon infusion? Since its prerequisite calls for the following:

Prerequisite: A simple or martial weapon with the thrown property

While understandably the infusion doesn't apply to weapons that don't have it by default such as Battleaxes or Greatswords, the feat specifically adds the thrown property to weapons that don't have it. Not "You may throw this weapon" semantic loophole that allows you to throw it but not make it a thrown weapon, but specifically gives weapons the thrown property.

Answer 1

This needs to work for the text to make sense

The infusion rules (p. 12, Tasha's Cauldron of Everything) say

Whenever you finish a long rest, you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item. An infusion works on only certain kinds of objects, as specified in the infusion's description.

You are the one infusing the item. If the item has the thrown property for you, then it meets the conditions for you and you can infuse the item. This wording is about a clean as it can get to make it clear that the weapon counts as a thrown weapon with the property for you and your class abilities, instead of just mentioning a "thrown weapon".

The "for you" restricts this to your actions and abilities. Another Artificer would not be able to infuse the item, as it does not have the property for them. There is no other interpretation of this language that makes sense: If the "for you" would mean that it somehow does not have the thrown property for you, then that aspect of the feat would not do anything.

The Thrown property is what allows you to throw a weapon in the first place. PHB, p. 147:

If a weapon has the thrown property, you can throw the weapon to make a ranged attack.

If the weapon did not have the thrown property for you, you could not even throw it to make a ranged attack (at least not as a normal weapon attack; you can throw anything as an improvised weapon, with the associated downsides, thrown property or no thrown property). That clearly would make this bullet of the feat utterly useless. If you however accept that the weapon has the property to allow you to throw it, why would it not have the property to allow you to infuse it? There is no reason to treat the two class abilities differently. Either it has the property for you, or it does not.

Answer 2

There is no way to determine a singular “official” answer

You can read “for you” as meaning it doesn’t count, or not. The language itself is ambiguous, and there is nothing available that will nail down definitively whether it is one or the other. You will have to ask your DM for a ruling.

Since thrown weapons are very much the neglected step-children of D&D 5e, I would recommend to all DMs that allowing this combo is the better ruling.

Answer 3

It probably doesn't work without houseruling.

Short version: "have the thrown property for you" does not fulfill the requirement "have the thrown property".

Long version: The benefit of Thrown Arms Master is "have the thrown property for you", which is equivalent to saying "only for you". The artificer infusion says the weapon must have the thrown property, which, going by the normal weapon property rules, is a property available to anyone. This means that the ability you have is more restricted than those that are listed in the requirements. You cannot use an ability if you don't meet all its requirements. By extension, if your abilities are more restricted than those in requirement, then you probably don't meet them.

This can be seen in the ability itself. Applying returning weapon gives the ability that "it returns to the wielder’s hand immediately after it is used to make a ranged attack". If you give it to another character, the weapon will have that ability despite not having the thrown property, which is contradictory. Is that an issue? I don't think so (just don't make a ranged attack, problem solved), but it points to the ability not being supposed to work that way.

As others have pointed out, it should not be an issue in normal use to allow this ability to work - but this would be handled as an exception, and with clear agreement on whether the player plans to use it for anything other than in conjunction with Thrown Arms Master.