D&D supports the notion of ranged characters. Not "snipers".
Of course a ranged character could and should stay out of the center spotlight. But that's not what we're discussing here. We're discussing a character that is effectively removing himself from the camera angle altogether. That is bad, because there will come times when you will need to present your own flesh and blood as a distraction for the monsters. Perhaps block a crucial movement so the monster doesn't bite the spellcaster when the tank is momentarily overwhelmed. Follow the party when the battlescene unexpectedly shifts. Etc
Not to mention the heroic angle. Why should the rest of the party accept that one character is always hundreds of feet away, and thus in relative safety? Especially since
none of your abilities actually require that. Staying out of trouble? Yes. Being far away. There is no reason.
Why? Because there aren't any snipers in D&D! All this talk about "snipers" make you think D&D is actually about that stuff.
Let me assure you that playing a "sniper" in D&D is a thoroughly suboptimal tactic. And it isn't well supported by the game either.
While it can be a fun character archetype to play, it really should not be encouraged in D&D. Best save it for a modern-era game. Especially with a newbie DM.
Now, you might think I'm accusing you of playing the game badwrongfun. I'm really not. I just need to ask you to stop labeling ranged characters "snipers" to the OP. It really gives off the wrong connotations. It justifies the behavior of that gunsmith of his. Based on what?
Other than the rule of cool - nothing. Again, nothing wrong with sniper player characters. Just save them for another game than D&D