You can easily foul the SKS a lot sooner than that. So obviously, they cleaned them routinely, just like any other military organization. Its really just a question of what their standards were, and probably a LOT lower than ours.
I imagine they would have a cleaning routine, but I doubt it utilized boiling water. Water is a precious commodity on a battlefield, and wasting fuel to bring the water to a boil would be silly. They'd clean the gun with the tools provided and lube with the oil bottle provided. If the corrosive primers tended to rust the gun out, oh well. Probably why they chromed the barrels...in order to withstand the rigours of war.


















































