A magazine is a source of ammunition. The term should not be confused with "clip" as they are not interchangeable.
With certain exceptions, the transfer of any magazine with a capacity of greater than ten rounds is prohibited by the Firearm Safety Act of 2013, which took effect on October 1, 2013. Violation of the law is a crime.
Possession of magazines of any capacity is not restricted under Maryland law with the exception of use in committing a crime.
There transport of a magazine of any capacity is not restricted within Maryland, except that those without authorization to carry (e.g. Maryland Handgun Permit, LEOSA, Armored Car Driver) must transport magazines enclosed, and out of reach. Maryland's Attorney General has issued an opinion letter that magazines may be transported loaded. The pre-loading of magazines is especially useful for those with a disability (e.g. those without fine motor skills) as well as those who are charged range time by the hour.
There are no restrictions on transporting a magazine of any capacity into Maryland, with the exception that those without wear & carry licensing must transport magazines enclosed and out of reach while within Maryland.
NOTE: Prohibited places, including school zones are not considered herein.