Yes , and there was a third occurance where Matrim Cauthon dreams of attempting to catch explosives while vast quantities continuously rain down on " massed pikes and charging horsemen." In the knife of Dreams( I believe it was in the chapter Dragons , and after Aldura demonstated a cannon prototype to Mat.)

Basically Mat has come up with very primitive gunpowder grenades and as for the cannon...

 

FROM WIKIPEDIA:

Fire lances", gunpowder-propelled arrows, were used in China from at least 1132. The first documented record of artillery with gunpowder propellent used on the battlefield was on January 28, 1132 when General Han Shizhong of the Song Dynasty used escalade and Huochong to capture a city in Fujian. In 1221, cast iron bombs thrown by hand, sling, and catapult were mentioned. Somewhere around 1249, the Chinese of the Song Dynasty began to load early gunpowder in the middle of thick bamboo as a projection firearm, firing clay pellets like a shotgun.

 

Around the time of the wars between the Mongols and the Song Dynasty (1268-1279), mortars with bronze tubes first appeared.[3] (However, the earliest certain example was dated 1332). Additionally, the Chinese and Mongols took up the use of "true" gunpowder instead of the slower-burning older mixture - which made this early cannon, known as the Huochong, more reliable and powerful. During wartime, the Chinese used the early gunpowder weapons in defence against the Mongols, mounting more than 3,000 bronze and iron casted cannons on the Great Wall of China. The weapon was later taken up by the Mongol conquerors, and also the Koreans. Many of the earliest weapons seem to primarily have functioned as psychological weapons, a trait gunpowder arms would keep for a long time.

 

From the early 14th century Chinese manuscript known as the Huo Long Jing, a passage refers to the first use of cast iron shell casings for gunpowder-filled cannon balls, fired by what the Chinese had termed the 'flying-cloud thunderclap eruptor' (fei yun pi-li pao):

 

The shells (phao) are made of cast iron, as large as a bowl and shaped like a ball. Inside they contain half a pound of 'magic' gunpowder (shen huo). They are sent flying towards the enemy camp from an eruptor (mu phao); and when they get there a sound like a thunder-clap is heard, and flashes of light appear. If ten of these shells are fired successfully into the enemy camp, the whole place will be set ablaze...[4]

 

Having an illuminator who is knowledgable of gunpowder ratios, Mat should be able to skip the firearm evolution process directly to high explosive powder for artillery with a fairly decent range.  Also, Mat would likely use explosive shells (having seen their effectiveness with the Dragon eggs) and stay away from solid shot.  I would predict a fairly quick evolution to the bronze cannons of the 16th/17th centuries known for excellent reliability, accuracy (when the crew is properly trained...no easy task) and durability (bronze is much more resistant to stress than cannons made of iron...problem is it costs 8-10 times as much)

 

 

I recall that there was a vision involving Matrim Cauthouns and Pins made out of man , as well as what sounds like gunpowder based munitions raining down on battle fields. Where was it I wonder? Perhaps its a fortaste of the carnage that Matrim Cauthon would inadverntly cause ( Possibily in Seanchan) after the Last Battle .

What about the gunpowder weapons introduced in the KOD?