fire (one's) pistol in the air
1. In a duel, to shoot one's firearm into the air to avoid injuring the other party. A: "Did I just hear a gunshot? Is the duel over?" B: "Sir Edmund fired his pistol into the air, so Master William is unscathed."
2. To avoid harshly criticizing or otherwise hurting someone during an argument or debate. I usually fire my pistol in the air in these sorts of debates—I hate hurting people's feelings.