According to the definition of assault rifle per Wikipedia:
Based upon this, any rifle that is just semi-automatic, and does not include selective fire modes, would not be an assault rifle.
So what’s the straight dope? Seems like there are confusing definitions used across the media.
The term used in the media is “assault weapon.” The distinction is important, since “assault weapon” has no firm definition.
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Different laws have different definitions. The 1994 Assault Weapons Ban (Public Safety and Recreational Firearms Use Protection Act) had a somewhat arbitrary definition of “assault weapons” that included certain types of semi-automatic weapons. The media may be using these criteria.
Warning: this topic often degenerates into GD/Pit content based on political considerations.
Wikipedia is technically right. A mere semi-automatic rifle is not necessarily an assault rifle. For instance, the M1 Garand is a semi-automatic battle rifle which doesn’t use an intermediate round, isn’t selective fire, and doesn’t use a removable box magazine… but is nonetheless a semi-automatic rifle.
The media isn’t always so technically savvy, and reports a non-assault rifle as an assault rifle out of a naïve assumption that any semi-auto rifle must be an assault rifle.
Also mixed up in this is the legal (and not technical) phrase “assault weapon”, which is a firearm with certain technical characteristics that don’t strictly overlap those of an assault rifle. It’s quite possible that the press would use “assault rifle” ignorantly assuming that’s exactly synonymous with “assault weapon”.
An assault rifle is is an intermediate caliber autoloading rifle with selective fire capability. An assault weapon is basically whatever some politician or media head wants to describe as this week’s Most Evil Weapon regardless of functionality.
Stranger
So with the exception of magazine sizes and cartridge calibers, are all semi-automatic rifles similar in their function? One pull of the trigger results in one cartridge fired.
Then the media and politicians will just have to use the preferred term for rifles like the M1 Garand: ‘Battle rifle’. 
Yep, that’s pretty much the definition of a semi-automatic weapon. It fires one round and automatically loads the next round, but it won’t fire the next round until you pull the trigger again.
Essentially, yes. There are details about the cycling system that differ between designs (gas piston, direct impingment, roller locking, delayed blowback) but there is really no difference in function between a wood-stocked Winchester Model 1907 and a Kalashnikov assault rifle (“AK-47”) in terms of how it operates for the user.
Despite what you see in movies and television, the use of fully automatic weapons in the commission of crimes is almost vanishing rare, and generally only by organized crime gangs who have the means to procure or modify such weapons. Nor is full auto necessary or even especially useful in most direct fire combat situations, to the point that nearly all militaries train infantry use in single fire and short (2- or 3-round) burst, with fully automatic fire reserved for suppressing fire provided by a squad automatic rifleman or fixed gunner. Most fully automatic weapons will empty a 30 to 50 round magazine in a few seconds under sustained fire, which means the shooter has to stop and spend that duration or longer reloading under fire.
Stranger
So the difference between an .30 caliber AR-15 and a .30 caliber Sauer deer rifle is amount of ammo held in the magazine and cosmetic detailing on the AR to make it look like a military weapon. The both are semi-automatic in their function.
That’s pretty much it. There’s a graphic around that shows the difference between a Ruger Mini 14 and an AR-15. The functionality is pretty much identical, the look is totally different.
This is technically correct (The best kind of correct!) however, with the advent of bump (aka slide) fire stocks available for guns such as the AR-15, the practical difference between semi-automatic and fully-automatic is virtually non-existent.
This video shows what a $99 stock is capable of. It looks fully automatic but it’s not.
Even better, these are all the same rifle. The mini thirty uses the same round as the AK-47, the others use .223, same as the AR-15.
Guess which one gets banned because it looks scary even though they all share the same lethality.
AR-15 platform rifles are usually chambered in .223 or .556. You can have different upper mods to chamber them in .22lr or even AR-10 platform for .308. There are more varieties as well. A deer rifle is typically bolt action in my mind, so a that would be substantially different than a semi-automatic rifle of any kind.
Some cosmetic features that are often found on an AR-15 platform rifle will add ergonomic comfort beyond mere asthetics. That’s based on user preference.
“AR-15” is a brand name, when the US Military buys them they designate them as “M16”. The two guns aren’t exactly the same today, particularly the civilian gun is semi-automatic and the military gun is fully automatic, though I’m sure there’s other differences.
If I can ask a question?
I have seen this debate all over social media as if it actually makes a real difference. A lot of totally innocent people got killed either way.
The media get this technical stuff wrong all the time, but when they describe a flat bed truck as a van, it really doesn’t matter to anyone but a pedant. Why does it matter that the weapon used in Orlando was or was not an assault rifle?
“Assault weapon” sounds scarier … “Varmint rifle” doesn’t make for a very good slogan. One would lose the whole “it’s specifically designed to kill people and only people” argument.
It only matters to me if people then form opinions on gun regulations based upon inaccurate information.
It matters because the difference can mean a person is a felon with a lifetime prohibition for firearms if they get it wrong.
