One of the men also faces charges including intentionally not registering firearms, incorrect storage of firearms, and neglect of a child.
Police executed a series of search warrants in the Nelson area in the last few days.
All of the weapons were loaded with rounds chambered and did not have their safety switches engaged.
Detective Inspector Albie Alexander said requirements around safe storage of firearms are just common sense.
"On a different day the police attendance at this address, rather than to execute a search warrant, could have been in response to a terrible and needless tragedy," he said.
Police were investigating the diversion of firearms - weapons purchased legally but then "diverted" into the possession of people without firearms licences.
Two of the men charged are or were, employed by a firearms retailer and used their position to facilitate the diversion of firearms, police said.
Police said they had identified at least 19 Alfa Carbine rifles purchased and diverted between October 2021 and May 2022.
The men face charges relating to the unlawful possession of firearms, dishonesty, and offences against the Firearms Registry and will appear in court 12 August.