Over the past 12 months the department said it had retrieved 6,500 guns issued to former servicemen after checking 309,000 files.
But thousands of soldiers have failed to return information about the equipment issued to them as required after their period of service ends.
The army said this week it was unable to contact 6,000 ex-servicemen because their current addresses are unknown.
An additional 4,000 veterans have failed to return their service records to the authorities.
The records include information about firearms and equipment issued to the soldiers.
The army said it would be issuing follow-up letters reminding veterans of the need to contact authorities.
In March, the army noted missing information in the records of 27,000 former soldiers who had served in the previous six years.
Subsequently, 17,000 of these have been brought up to date.
The army said it is aware of 300 men who have failed to disarm after being notified to do so.
The cantons, which have received a list of names from the army, are aiding the defence department in its bid to track down these people.
Normally, soldiers who have completed their service are required to return firearms issued to them within 60 days.
In Switzerland, men between the ages of 19 and 34 are subject to military conscription, with alternative service for those found to be unsuitable for duty.
Around 20,000 conscripts receive 18 to 21 weeks of training each year.