The anti-bikie Echo taskforce and Dandenong detectives executed warrants in Springvale and Narre Warren South at 5.30am, arresting four men and three women.
The group were still in custody at midday.
A tattoo studio on Springvale Road, Springvale and a home on Padstow Street in Narre Warren South were among the properties targeted, Senior Constable Melissa Seach said in a statement.
Fairfax Media understands at least 12 guns were seized, as well as ammunition, as part of an ongoing operation.
The operation was expected to continue throughout the day.
The Comanchero's South Melbourne club house was raided by heavily armed police six months ago as part of an investigation into an attack on a man who had tried to leave the gang.
In October, Fairfax Media revealed almost half of the Comanchero, including senior members, were behind bars.
At the time, Echo's detective superintendent Peter De Santo said about 32 of 70 Comanchero in Victoria were in custody due to raids.
More to come.