Officers searched properties in Sefton and Knowsley before 07:00 BST as part of their investigation into drug dealing and organised crime.
Eight people were detained in Bootle, Kirkby, Waterloo and Maghull, while a further two men were "produced from prison", Merseyside Police said.
A shotgun, handgun and a large quantity of Class A drugs were also seized.
Supt Claire Richards said the success of the raids would help reduce gun and gang crime in the area.
She added that the raids came as a result of information from the public being "pieced together with a number of police enquiries".
Ten people have been arrested and two guns seized in a series of police raids on Merseyside.