100mm cannon has far heavier recoil since not only size as also not being automatic cannon.
So maybe they are developing 100mm autocannon.
the higher caliber North Korean naval artillery is centered around the 85mm and 100mm, certainly the 76mm with western ammunition would be an extreme change.
For this reason, some hypotheses have appeared in the past
1) The 76/62 clone adapted to the Russian-Chinese ammunition used by the 76.2 mm AK-176 / PJ26 which would thus lead to a standardization and if necessary (conflict) to receive the ammunition from friendly countries
But in any case, if you don't want to buy ammunition from friendly countries, you need to create an internal production line, as also if you use western ammunition for the 76mm (in this case it will not possibly be able to receive any from neighboring friendly countries).
2) Another hypothesis that has been expressed in the recent past is that the clone of the Oto Melara Compact, the caliber of the weapon has been increased to 85 mm, capable of using the standard ammunition currently in use on weapons of the same caliber used in the DPRK for both direct fire and air defense purposes (85mm 90K / 85mm 52-K)
note the similar dimensions of the shell case
Instead the 100mm uses much larger ammunition and it would seem difficult to adapt the loading system of the Compact for that ammunition, furthermore it would be necessary to strengthen each component to resist the increased recoil force during firing and at high rate of fire, this brings me to exclude that the Compact clone can be brought to 100mm.
Lately Kim Jong Un has delighted us with numerous news relating to weapon systems, perhaps he himself could soon reveal the characteristics of that naval cannon similar to the Compact with which he had himself photographed.