Well, according to the table, the answer is yes, but not in the way you'd like it. The way it's written makes it sound more like for raid weapons, you can only exchange for 1 copy per month (at 2 ori each). On the other hand, the exchange exclusive weapons are limited to just 4 (1 ori per), so if you want, you could just burn 4 ori right away for a 3* copy of one of those. A desperate enough fire main might as well go for that gun.