McCartney taped the message for Voices Against Violence, a campaign started by singer Tony Bennett and his son Danny, E! News said.
Those who text "MYVOICE" to 877877 will get an automated message from McCartney after which the caller is connected to a U.S. congressman's office.
"Hi, this is Paul McCartney, and in a minute you will be connected to a congressperson who needs to hear your voice, now. Tell the congressperson that you support commonsense laws that keep guns out of the hands of the wrong people, including criminal background checks on all gun sales," McCartney said.