A CRACKDOWN on airguns has been launched in Calderdale.
Police are warning owners of self-contained air cartridge guns that their time is up if they don't have a firearms certificate.
Anyone found with such an airgun and without the appropriate police firearms certificate faces a five-year prison sentence for possessing a prohibited firearm.
Chief Insp Steve Cotter said: "I urge people to hand in such weapons if they don't have a certificate."
Nationally such weapons were used in at least 80 serious crimes - including murder - between 2001 and 2002.
The ban applies to any air rifle, airgun or pistol that uses, or is designed or adapted for use with a self-contained gas cartridge system.
It does not apply to weapons that use a CO2 bulb system, because CO2 bulbs do not contain a projectile and are therefore not self-contained.
"We don't want weapons of this nature to fall into the wrong hands," Chief Insp Cotter added.
"People who have them must understand what they are letting themselves in for if they haven't a valid certificate."
Anyone with concerns as to whether or not their airgun is legal should phone the police firearms licensing department on 01924 292330.