The Ministry of Supply began using Site 3, to the southeast of Eastriggs, in the 1930s for ammunition storage. The site was known as CAD Eastriggs. Ammunition was transported from the storage bunkers within CAD Eastriggs using a narrow gauge railway system. Two of the petrol locomotives were used on the Duchal Moor grouse railway near Kilmacolm in Renfrewshire. The site was connected to the Glasgow and South Western Railway at a junction at Eastriggs. In the 1960s, CAD Eastriggs became a sub-depot of CAD Longtown.