Gun licence holders and retailers are being asked by West Midlands Police to hand in their replica weapons.
The amnesty comes to an end on 30 April
The call comes during a month-long nationwide weapons amnesty, which has been set up to encourage people to hand in firearms without fear of prosecution.
The force, which has written to all gun sellers and licence holders in its region, has also requested that BB guns and air weapons be given up.
The letter warns that efforts to reduce the number of genuine firearms getting into criminal hands have been successful, but says there has been a rise in the number of blank-firing guns in criminal use as a result.
Blank firers can be converted to discharge ball bearings, and a small proportion of shots fired from these converted weapons have killed people.
Acting Detective Superintendent Jon Hesketh there was no good reason to own such a gun.
"The use of these items as weapons not only creates considerable fear on the part of the victims and the public, but also places the person in possession of them - often a young person - at risk of confrontation with armed officers with potentially fatal consequences.
"We all take crime and the fear of crime very seriously and our aim is to create a safer community by reducing the criminal use of firearms."
The government is planning new legislation making it an offence to possess a replica firearm or air weapon in a public place without reasonable excuse.
The firearms amnesty was launched on 31 March and runs until the end of April.