The year 1860 comes to mind.
5.56mm
The government needs to disarm the population before the real crisis begins. When America’s economy finally collapses, the cities are going to become ungovernable and the government is going to force people into the countryside as the only means of feeding them (Can you imagine what Chicago would be like with no jobs and no working infrastructure? The 1930s riots would look like a picnic). And the only way they can do that is to seize the land of those who already live in the rural areas. At the point of the gun if necessary.