Corrections

To whom is may concern,

I realize that the recent tragedy has brought gun control to the forefront of American political discussion, and I think what you were trying to do with this article is admirable.  If we're going to have a serious discussion about this, we should all be informed on the subject.  Unfortunately, the article contains a lot of misinformation, and I think it could lead to many people who are depending on your website to learn about firearms being misinformed.  Rather than getting involved with the bickering in the comments section, I thought I would lay out a few of my concerns here in the hopes that you can correct the article shortly.

1)  However, most gun experts agree that fully automatic firearms (defined below) count as assault weapons, as do some higher-caliber semi-automatic guns.
I've never met anyone who uses this definition.  While legal definitions do vary between states, an assault weapon is not high-caliber.  Assault weapons fire what is known as an "intermediate cartridge".  This means that it is between a pistol round and a rifle round in size.  Common examples include .223 (caliber), 5.56x45 (mm), and 7.62x39 (mm).  Also, not all fully automatic weapons are considered assault rifles. For example, neither sub-machine guns, nor machine guns are considered assault rifles despite being fully-automatic.

2) Different grips and mounts can modify the power and accuracy of a semi-automatic gun
This is completely wrong, and I'm not sure where your writer was coming from with it.  A grip or a mount cannot change the power of any gun.  The power comes from the ammunition.  As for accuracy, neither a grip nor a mount can change the inherent accuracy of the gun.  However, they can be used to make it easier to hold or give a more stable shooting platform.  This would make you more accurate, but not the gun

3) Well-known examples include machine guns, which are automatic firearms mounted to a wall or rail in order to increase stability and accuracy
This is not necessarily true.  While machine guns are generally quite large and unwieldy, they do not need to be mounted in order to operate, and are usually portable to some degree.

4) submachine guns, which are portable
As I said in #3, machine guns are not inherently immobile.  So, portability isn't a good way to differentiate sub-machine guns and machine guns.  Sub-machine guns are distinguished by the ammunition they fire.  Machine guns fire a larger round, while sub-machine guns fire a pistol cartridge, like 9mm.

5) no handguns would ever be considered an assault weapon
While most firearms expert's definitions of an assault weapon (intermediate cartridge, etc) would not encompass handguns, many legal definitions which use magazine capacity as a determining factor could.

6) A common type of handgun is a pistol, a small firearm with a single, nonrevolving chamber.
What is described here is an auto-loading pistol, and doesn't describe all pistols.  Revolvers are still considered pistols.

7) No revolvers are semi-automatic
I suspect this is just a typo, and that your writer meant that no revolvers are fully-automatic.  All revolvers are semi-automatic.

8) Firearms with a groove carved into the barrel walls to give bullets spin. (This is why rifles often have long barrels: to give spin to bullets.)
While the grooves in the barrel are called "rifling", they are not unique to rifles.  Nearly every firearm, with the notable exception of shotguns, has a rifled barrel.  A better definition of a rifle would be a firearm which has a rifled barrel, and is fired from the shoulder.

9) In the Aurora shooting, James Holmes used an AR-15 which he had purchased legally on the Internet but for which he had not acquired a permit in Colorado.
I'm not familiar with CO's specific gun law, but to my knowledge, only an federally licensed firearms dealer can receive guns shipped from the internet.  It is still possible to buy a gun on the internet, but it must be shipped to an FFL who then takes ownership of the gun.  After this, you can have them transfer it to you, but still need to go through any legal measure needed to buy a firearm from an FFL normally.  The way your article is phrased makes it seem as though it is possible to buy an AR-15 on Amazon and have it shipped to your door without the proper legal measure that come with buying a gun in a store, and this would be misleading to people unfamiliar with the process.

I hope this e-mail has been constructive, and that you will make corrections to your article.  While I have done my best to provide you with accurate information, I think it would be prudent to have my responses fact-checked as well (and hopefully with a little more caution than in the original article).  I hope that the debate about gun control can be a constructive and well-informed one, and that your revised article can facilitate that.

Sincerely,