From a financial point of view, yes, hunting is the main reason.

And from a motivational point of view: the 1994 report [sorry I can't find anything more recent about gun ownership with a quick search] https://www.ncjrs.gov/txtfiles/165476 states: “The most common motivation for owning firearms was recreation.”

And from a numbers point of view: that report says “44 million Americans owned 192 million firearms, 65 million of which were handguns.” – so about two thirds of the weapons are shotguns and rifles. Those are hunting weapons.

It then goes on to add: “Forty-six percent possessed a gun primarily for protection against crime.” – the high number there probably being at least partly explained by their data point “Sixty-eight percent of handgun owners also possessed at least one rifle or shotgun.” – so while those 68% “possessed *a* gun primarily for protection”, they mainly had and used guns for recreational purposes.

Another way to look at it, is what they get used for: guns are used defensively in between 0.1M and 2.5M cases per year (numbers vary wildly depending on sources). Most of these don’t even involve a shot fired, but let’s pretend they all fire a dozen shots. So that’s maybe 24M rounds/year used defensively, at an absolutely insane maximum. For comparison, the US military uses 70M rounds per year.

While I can’t find any hard figures for US ammo sales in a quick search, it looks like the number of rounds sold each year is orders of magnitude above that. For ATK alone “Annual Sales of “Hunting and Sporting” ammunition alone total $750,000,000.”  That’s half its annual sales, and it makes 6.5Bn rounds per year.  …but all that includes international sales, too, which means I’m not comparing like with like, I’m afraid. Good numbers are hard to find :(

Still: clearly not even in the same ballpark.
http://bulletin.accurateshooter.com/2008/02/atk-is-1-ammo-maker-with-15-billion-in-annual-ammo-sales/

A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed.

Technically, the right to own guns was to protect non-military, non-criminal people from military and criminal people, who have all too often in history been the exact same people.  See: highwayman, brigand, brownshirt.

Some of your fellow Europeans get it, and do it much better than we USians do: Swiss gun politics

Sadly, this would be a rather good weapon or choice for terrorists, assassins and murderers.

Uproar and overeaction ensues, followed heavy regulation swept-in in a panicked rush because too few people yet have seen or understand the potential benefits of this technology.

So I don’t blame the 3D printer company at all for wanting no part of this guy’s project. 

It is perfectly legal under federal law in the US, and under state laws in Texas, to build yourself a pistol, rifle, or shotgun (basically anything but a machinegun, although you have to pay a federal $200 tax first before building suppressors, short barreled rifles or shotguns, AOWs, or Destructive Devices).  You can even sell it eventually (or give it as a gift), you just can’t make them to sell for a profit.  For that you need to have paid a federal Special Occupancy Tax, I think it’s $1000 a year, might be more, it’s been a while since I looked it up.  As a rule of thumb it is advisable not to sell any gun you make just because why stick your hand in the hornets nest if you don’t have too, right?  Remember, the ATF used to follow people at gun shows, and when they bought a gun for say $100, come up and offer them $120 for it, and if they accepted arrest them for selling guns without a Federal Firearms License because they’d made a profit by selling guns, and you need a FFL for that.  

This “project” sounds like a hoax from end to end- was the goal to print a 3D gun, or to stir people up?

Thanks, assholes! You’ve derailed a world-changing technology because you just couldn’t wait to have shitty, worthless guns. Great job.

there are dozens of millions of gun owners in the USA, and the vast, VAST majority of them are totally trustworthy people who do no harm with their weapons. that fact in itself is pretty powerful support for the right to keep arms.

I seriously wonder whether some people love their guns more than their children.

moral: there is only one true weapon, and that is a sapient mind that’s set on doing harm. everything else is just tools.

The legal basis of the constitutional right to arms is the 2nd amendment which has nothing to do with hunting, a secondary activity with firearms (especially now).

Military rifles and civilian rifles do not differ in any militarily significant manner.  Both fire bullets at an adequate rate relatively accurately.  It would be more accurate is to say that civilians don’t have ready access to crew-served weaponry, high-grade explosives, armored vehicles, and military aircraft (or even aircraft at all for the most part).  
Fighting the government would definitely be a costly proposition, but not impossible because … numbers; current military strength equals about one million; population equals about 310 million most of whom are armed or could be pretty quickly.  Also, lots of military will not shoot U.S. civilians in general revolt.

Actual armed revolt would bring down the government pretty quickly because our government is not structurally set up to be in opposition to the people.

As for the tired argument of people killing people, while it is true, the guns help. A lot. Since you can’t really regulate the presence of people in a society, you might consider regulating the availability of guns, and make it a little less easy for the people to kill each other in the “heat of battle.”

[Edited to make it less preachy--made it worse.]

Now yes, if you don’t actually go out into areas that have such animals, then you generally have no need to arm yourself to defend against them, but if you are going out to such areas, be it for fishing and/or hunting to put food on a table or, ugh, recreation, then you should at least be prepared for the worst.  If you can’t tell, I don’t like the idea of people killing animals for “sport,” mostly cause it’s a waste of good food.

Oh, and a momentary reality check: Sigh. Guys like this are dangerous idiots. But inevitable. How sad.