Anyway, I'm sorry about my theory about Gin having a fast reflexes to avoid the drug in the needle. I really forgot that part and I rewatched it and I was wrong. Gin felt weak (I think..?) and fell on his knees when the dart hit him.
I don't think it was the clothing. If you noticed, Gin was still affected by the tranquilizer but he just didn't fall asleep instantaneously.