Spotting scams is something everyone in the gun community should be aware of by this point. A few obvious things to consider:
Do they sell stuff that you can't legally buy?
Do they have stuff in stock that nobody else has (eg primers that nobody else has)?
Do their terms of service mention a different business? (eg These guys mention SFRC in the Returns section)
What are their payment options? If they don't take credit card, thats a red flag. If they DO take bitcoin, thats a red flag.
What is their contact info like? Do they have a phone number? Email? Physical address? When you put their physical address into google maps does it seem like a place where a gun store could be?