Compressed air has been used since the 19th century to power mine locomotives and trams in cities such as Paris (via a central, city-level, compressed air energy distribution system), and was previously the basis of naval torpedo propulsion.
What’s old is new, again.
Lewis and Clark left Pittsburgh - where I live - armed with air rifles. The demonstrated one on an island in the Ohio river near the city.
At least one person suffered serious injury from the bullet.
The weapons were useful for hunting but not all that accurate. At least they didn’t waste powder.
Great ideas but not always a practical solution.