Semtex packed into a mortar device and other explosives were among items recovered during a major police operation against dissident republicans.
An automatic weapon with a silencer and ammunition was also seized during the raids.
The searches in south Armagh and east Tyrone took place over the Easter weekend but details of the weaponry discovered have only just been released.
Police said they found a horizontal mortar containing more than 0.5kg of Semtex, another 0.5kg of Semtex and three timer power units.
They also found 25kg of home made explosives, an automatic weapon, a silencer and ammunition.
The searches were carried out hours after three men were arrested in Keady, south Armagh on Good Friday over another arms find.
They have since appeared in court charged with a series of terrorist offences, none of which is linked to the haul discovered.