Trading gunfire is such a weird phrase

I think expressions like this have their origins in trading/exchanging arrows, because in many sieges and battles, you literally picked up the missed enemy arrows once you ran empty.

But it doesn’t make sense for bullets.

Bullet bartering

Gunfire free trade agreement

police terms are so silly, I think they call scratching a cop car paint swap or something

edit: trading paint

Bombardment marketplace

It’s a classless, moneyless gunfight.

Unequal Exchange