The militia in those days were pretty organized. They drilled together far more frequently than most shooters do today. Their shortcoming against the militia were very short terms of service when called up, resupply, operating in conjunction with a larger force made up of similar units, and fighting over who was in overall command.
The Founders had no issue with private ownership of firearms I'm sure but the 2nd Amendment was about the militia and people don't understand how that system worked.
Indeed. The concept of the militia is central to the understanding of the 2nd Amendment. As you say, the Founders didn't care about the general, private ownership of firearms. That was a given in 1791. What they
did care about was the civic right of the militia to be armed.
We have to look at what the militia was like in 1791. There was a "general" (universal) militia in every state, in which, theoretically, every free male citizen of military age was enrolled. They were supposed to have periodic (annual?) musters at their county seats, bring their own weapons, have their weapons and equipment inspected, and undergo some rudimentary military training. But this never really worked out in practice. The musters, on the rare occasions when they were actually held, quickly deteriorated into drunken parties on the courthouse lawn. The fact is, the early Americans were too busy with their private lives, and in the absence of an immediate threat, they didn't take their militia obligation seriously.
So the militia quickly devolved from the "general" militia to a self-selected "volunteer" militia. These were basically military hobbyists who formed themselves into local units, and then applied for state sanction. These volunteer units were supplied arms and equipment from the state governments, which in turn were allocated arms and equipment from the National Armories and other federal installations, according to a set formula.
The War of 1812 was a mess, fought by a disorganized mixture of general and volunteer militia, along with small numbers of Regulars. Thereafter, the general militia was abandoned. The Mexican War and the Civil War were mostly fought by units of volunteers.
The point is, the volunteer militia was centrally supplied. The members no longer had to provide their own weapons. The 2nd Amendment's direct application to this militia therefore became moot. By, say, 1820, the 2nd Amendment was a dead letter as regards its original purpose, which was the private arming of the militia. And then it sat dormant until it was resurrected in the 20th century as the foundation of a private, individual right.
But the big mistake was Justice Scalia's treatment of the Militia Clause as a nullity, in the
Heller decision. What he should have done is recognize the
idea of a universal militia (even though it didn't exist in practice), and then base the right to private arms on putative (theoretical) membership in such a militia. That would have meant that we were all entitled to own the latest weapons in use by the military. Clearly, that would have invalidated the NFA, for example. The 1939
Miller case merely hinted at this.