I'm trying to make a set of armour with a built in ranged attack (not a spell).

I can't see how to do this on a homebrew item, can anyone shed any light on how this would work?

Probably easiest to call it a spell. You can make a spell attack with dex or strength as the "casting" ability. There would only be a difference if you were in an anti magic field or something and you can make a note about that

Actions cannot be added to magic items yet. You would have to:

• Create a spell to count as the attack.
• Create the item as a weapon and add an AC boost to it.
• List it as plain text and let the player create a custom action on their character sheet to represent that attack.

I always check existing things that do what I'm trying to do. How does demon armor add its weapon attack?

Quote from DxJxC >>

I always check existing things that do what I'm trying to do. How does demon armor add its weapon attack?

 It doesn’t.

Quote from DxJxC >>

I always check existing things that do what I'm trying to do. How does demon armor add its weapon attack?

 It is a feature stated in plain text. It doesn't affect your character sheet.

So you can do that and just have the players play it that way or create it as a weapon and give it +AC bonus with the caveat that it is armor. 

Quote from IamSposta >>

Quote from DxJxC >>

I always check existing things that do what I'm trying to do. How does demon armor add its weapon attack?

 It doesn’t.

 Then the answer is "you can't" and you have to just say it or work around it.

I don't know why items can't add actions yet, everything else can...

They haven’t programmed them to have actions yet. 🤷‍♂️

And I already knew the answer, that’s why I wrote this earlier:

Quote from IamSposta >>

Actions cannot be added to magic items yet. You would have to:

• Create a spell to count as the attack.
• Create the item as a weapon and add an AC boost to it.
• List it as plain text and let the player create a custom action on their character sheet to represent that attack.