Firearms officers and a police helicopter were despatched after reports of gunfire - and discovered a clay pigeon shoot.
Derbyshire Police went to disused slurry pits near Mapperley, Ilkeston, after a nearby resident called 999.
Shoot organisers are now being urged to contact the force with event details.
Insp Jock Munro said: "The call we had alerting us to the sound of shots was made in good faith by someone who was genuinely concerned."
The site was deserted when police arrived.
But after making extensive inquiries, they discovered guns had been used at an organised clay pigeon meeting.
Insp Munro said: "We would really appreciate it if the organisers of shoots would let us know what has been arranged.
"If we had known about the event we would have been able to reassure the caller.
"It would also have prevented us from spending time and resources investigating the incident."