Hmm. Your word is law. I'm just the adviser.
But I'd say that I suppose its acceptable. A little more detail might be helpful, but there's nothing openly against the rules.
However, isn't the actual storyline (the Throne of Glass books which this RP is based off of) set in a time when there's no such thing as a firearm? Since we're so true to the storyline as far as other characters, as far as other magics, why should we allow firearms?