One of the arguments that gun control advocates are fond of bringing up is "The Founding Fathers couldn't possibly have anticipated automatic [or, sometimes, semi-automatic] weapons." This assertion is then used as a rationale to justify why the Second Amendment "can't possibly" apply to automatic or semi-automatic weapons.
Let's examine this argument.
To begin with, we should probably briefly recap the history of repeating arms. A good place to start is probably the ribauldequin, an early volley gun first documented in 1339. Drawings by Leonardo da Vinci for such arms exist. These are not technically repeating arms; they fire all of their barrels at once (hence the name "volley gun"). From volley guns, though, we move on to the pepper-box revolver, a firearm having a rotating cluster of three to six (or sometimes even more) muzzle-loading barrels. The earliest such weapon documented to exist is the Stopler revolving arquebus of 1597, a matchlock weapon whose barrels were rotated by hand. Flintlock pepper-box pistols can be documented to at least 1790, although self-rotating percussion-cap pepperboxes were not fully developed until 1830. From this we could reasonably conclude that the Founders were probably at least aware of the possibility of repeating arms.
But wait! While the pepperbox was evolving out of Stopler's revolving arquebus, something rather more dramatic happened in London in 1718. In that year, James Puckle invented his Defence Gun. This weapon, which has become known since as the Puckle Gun, was a hand-cranked flintlock revolver cannon of 1.25" bore with interchangeable cylinders, capable of firing 63 shots in 7 minutes. (It came with round-bored barrels and cylinders for shooting at Christians, or square-bored for shooting Turks.) It was not a commercial success, but is considered by many to be the first prototypical machine gun, although the mitrailleuse (technically a volley gun whose barrels could be fired sequentially instead of in a volley) and the Gatling gun (which has a better claim to be the first machine gun) did not appear until 1851 and 1861 respectively, and the machine gun in its modern form was not invented until 1884 (by Hiram Maxim).
Was the Puckle gun or some relation thereto in military service in 1776? No. But is it likely that the Founders knew of the possibility of such a weapon? It seems unreasonable to insist at that point that they could not have been aware that such things existed, nor that they could and almost certainly would be improved upon in the future.
But this, honestly, is a side issue. It is pointless to speculate upon whether the Founders foresaw, or could have foreseen, specific technological developments. I can almost guarantee you that they did not attempt to. But this we know: They knew that the world would change in the future, and that knowledge would continue to advance. Could they have predicted the modern digital computer? Almost certainly not. Supersonic jet fighters? Equally unlikely. But between the Revolution in 1776 and the ratification of the Constitution in 1789, Pilâtre de Rozier made the first manned flight in a hot-air balloon, an event of which it is highly unlikely they remained unaware, so they surely must have known that the age of flight was dawning. The Founders were educated men; they did not know in detail what changes the future would bring, but they knew that it would bring change. And in all truth, if the question ever arose, the Founders probably realized that if Americans ever had to defend themselves against attackers carrying advanced weapons that didn't exist in the last quarter of the 18th Century, it would probably go better if they had the same weapons themselves.
So what did they do in the Constitution to "future-proof" it?
Well, basically nothing, except to provide for a mechanism for amendment. They trusted their successors to make what changes to the Constitution became necessary, as and when they became necessary. They did not attempt to predict the future, nor to second-guess it. But at the same time, they did not see fit to restrict any of the provisions of the document they had created to only the world as it then existed.
You see, the Founders knew that the world would change over the years and centuries to come. But they also knew that some things which they believed about the world would not change: that the people would always be entitled to "life, liberty, and the pursuit of happiness"; that the people would always have a right to follow a religion or not, as they choose; that the people would always have a right or protection from arbitrary search and seizure of their property without due legal process; and that the people would always have a right to defend themselves against attack — by outlaws, or by foreign invaders, or even by their own government, should it lose its way and become oppressive and tyrannical.
These rights can be restricted by a government, under threat of imprisonment or force of arms. Their exercise can be outlawed by a tyrannical government. But they cannot be withdrawn or revoked by it, because they are not granted by it in the first place. The Founders asserted that these "inalienable rights" came direct from God and were beyond the authority of men or their governments to grant or withhold, and that the rights they enumerated in the document they created were not thereby granted or created, but merely acknowledged and recognized.
The Founders stated what they saw to be self-evident; and they trusted their successors to maintain what they had created, and provided a way for their successors to make such changes as they deemed necessary. Such changes have been made, again and again. Remarkably few of those changes have been failures (Prohibition, anyone? We have Prohibition largely to thank for organized crime in the US). The majority of them have been noble changes that increased freedom. The thirteenth Amendment abolished slavery. The fourteenth overruled the Dred Scott v. Sandford decision and granted full citizenship to persons of African descent. The fifteenth abolished restriction of suffrage by race, and the nineteenth abolished restriction by gender. The twenty-fourth prohibited withholding voting rights for non-payment of poll tax. The twenty-sixth extended the vote to age 18 and older.
So, no; the Founders, as far as we know, did not specifically anticipate modern automatic weapons when they drafted the Second Amendment.
But that doesn't matter.
Why doesn't it matter?
Because it is unreasonable to assume that they did not anticipate that the sophistication of arms would continue to advance in the future as they had seen it advance in their time, yet they did not see any need to restrict the Second Amendment to exclude such advanced future weapons. They trusted their successors and dependents with whatever the future might hold. They saw no reason why they should have to restrict the ownership of weapons that hadn't been invented yet, because — even though they knew that criminals existed then as they do now — they trusted the bulk of the People to act wisely and responsibly.
And on the whole, the People have lived up to that trust.