Ontario provincial police say the raids conducted at CFB Borden and several locations in Quebec netted hundreds of firearms, gun enhancements and parts, including silencers and thousands of rounds of ammunition.
They say officers also seized documents related to the production of prohibited firearms parts and enhancements, as well as a computer, several portable drives and a vehicle.
OPP say the parts seized would have allowed buyers to convert semi-automatic guns into fully automatic ones, or use over-capacity ammunition magazines.
Quebec provincial police, the Department of National Defence and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives also took part in the investigation.
David Theriault, 36, of Lyster, Que., faces multiple charges including importing or exporting firearm components, importing or exporting firearms and trafficking in firearms, weapons, devices or ammunition.
Police say he is also facing charges in the U.S., including importing machine-guns without a licence and smuggling.
"This investigation is another clear and strong message that gun smuggling, the manufacture and distribution of firearms enhancements and their inherent dangerous criminal activities will not be tolerated," OPP Commissioner Chris Lewis said in a statement.
Authorities say the investigation continues and more charges are pending.
Theriault is being held in Ontario and is scheduled to appear in court in Barrie on May 2.
Note to readers: This is a corrected story. An earlier version incorrectly said police raided CFB Trenton.
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