For the US, I posted an answer here.

In the pre-industrial world armories were necessary to be able to produce enough weapons for an army, as production was a big challenge and there had to be some standardization- muskets had to be the same caliber, and concentrating lots of skilled labor in a place where energy resources ( like water power) and materials ( like coal, iron ore) made very good sense. In the 20th c., it was no longer necessary to get weapons manufactured in one big facility- transportation could move materials, energy sources were no longer limited to location, and mass production methods had become standard industrial practice, so Remington or Smith Corona could make 1903-A3 rifles to specification just as well as Springfield. It was also very difficult for one facility to produce enough: Springfield could not produce enough rifles for WWI , and the Italian armory at Turin, unable to make enough Carcano rifles, was forced to re-work old Vetterli rifles to use modern 6.5 mm ammo.

In the end, having a government facility make rifles became as outdated as having a government facility make fighter planes, heavy tanks, guided missiles.....the armory was replaced by the military-industrial complex.