Suppose that the government required you, as a citizen, to perform military service regardless of your consent. Also, they required you to provide weapons and ammunition to government specification at your own expense, and present it for regular inspection.
Also, by you, the government meant a free, white male of military age.
This is what the Congress that passed the Militia Acts of 1792 thought necessary for a well regulated militia.
A few observations.
By well regulated, they didn't mean restricted by law. They meant something more than that. They meant to produce a militia that was militarily efficient, sufficiently trained that they could fight effectively as units on the battlefield.
Second, to avoid the possible evil of oppression by a standing army, they were willing to subject virtually the entire population that mattered to the contemporary mind to compulsory military service and compel them to arm themselves at their own expense.