The men, named as Julian Steele and James Davis, were paraded at a news conference which heard that they were detained while driving through Kabul and told police they were working for a private security company, Garda World.
"The detainees did not have any documentation for carrying weapons, so we have charged them with illegal smuggling of weapons and have handed them to the attorney general for further investigation," said spokesman Sediq Sediqqi.
"The National Police hereby also announce the dissolution of this company, and based on the order of the interior minister, the head and other officials of this company will be summoned to give account. The company has been dissolved."
Two Afghan nationals travelling with the men were also detained. They were also shown to the media along with the weapons, but all four men stood with their backs to reporters.
Afghanistan is home to thousands of foreign private security personnel providing services for foreign troops, diplomatic missions and aid organisations.
But relations with the authorities have deteriorated. President Hamid Karzai accuses the firms of breaking the law and taking business away from Afghans.
Perceptions that those working for security firms are little more than gun-toting mercenaries, roaming the countryside with impunity, have made them deeply unpopular among Afghans.