I was at a gunshow this past weekend.  One of the vendors had a large sign proclaiming "M-16 upper receivers on AR-15 lower receivers."

I thought this was illlegal.  Am I correct?

Brad

Believe that might depend on whether they contain the M-16 B/C group.

Mike

you can have a M16 upper on a AR15 lower, as long as you dont have any M16 parts on the inside, you cant have a M16 lower.... Bluemax

The difference between an M16 upper and an AR15 upper of the same general configuration is only the bolt carrier's design.  That's it.

And, yes, you CAN legally own an M16 lower receiver or even a complete M16...IF you file the appropriate paperwork, pay the taxes, find one to buy that's transferrable, etc...

CJ

Despite what the folks over at Bushmaster might be telling people, I don't believe the law prohibits the possession of an M-16 bolt in your upper.  I would not do it (what's the frikin point), but one bolt does not make an AR readily convertible.

Troy, I think that's a myth.  I've attempted to get an opinion letter on that before without success.  Do you have a letter?  If so I will gladly stand corrected (as to their opinion), however, the code section is not ambiguous as written.  If a BC could "readily convert" an AR into a MG, it would consititute a violation.  As we all know, that's not the case.

As usual, I would not recommend it.  Again, what's the point.

Here is the best that I could find:

[url]
http://www-2.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/atf_letter52.txt[/url]

[url]http://www-2.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/atf_letter55.txt[/url]

[url]http://www-2.cs.cmu.edu/afs/cs/user/wbardwel/public/nfalist/atf_letter90.txt[/url]

mark

I could only download the last two letters.  Both of them support my point.  Both state, in pertinent part, that the prohibition centers on whether you possess enough parts to assemble an unregistered machine gun.

From the second letter:

"we stated that an individual, who possesses a registered M-16 machinegun, certain AR-15 type automatic rifles and M-16 type fire control components may have a combination of parts [red]from which an additional and unregistered machinegun can be assembled[/red].  We therefore strongly advise against the stockpiling of additional M-16 fire control components."

The "advice" is an admonition not to "stockpile" M-16 components because, obviously, you could eventually have enouph parts to assemble an MG.  

Again, one BC in an AR does not a readily assembled MG make.

From the third letter:

"The definition of a machinegun in section 5845(b) also includes any combination of parts from which a machinegun can be assembled if such parts are in the possession or under the control of a person.  Thus, an AR15 rifle possessed with separate M16 machinegun components can meet the definition of a machinegun, [red]if the rifle shoots automatically when the components are installed.[/red]"

Same principal.

They go on to give the same "advice" as in the other letter.

No where does the ATF take the position that one M-16 part (not capable of converting semi to FA) is illegal to possess in the presence of, or installed in, an AR.

However, as before, my "advice" is similar to theirs'.  Don't do it.

In order to make an AR-15 Full-Auto you would need to have a certain combination of parts.

For proper full-auto it is the Hammer, Trigger, Disconnector, Selector, Auto Sear, and Bolt Carrier.

For unsafe Full-Auto, you can simply use a Selector, Trigger, and Disconnector.

You could also make it Full-Auto by simply removing the disconnector. Of course this would be highly unsafe.

So, my guess would be that the following combinations would be illegal:

1) Hammer, Trigger, Disconnector, Auto Sear, Selector, Bolt Carrier, AR-15.

2) Disconnector, Trigger, Selector, AR-15.

3) Auto Sear, Bolt Carrier, Hammer, AR-15.

4) DIAS (Any), AR-15.

If you remove the disconnector from the AR-15, you wind up with a single-shot firearm.  Even if you put in an all M16 parts (except an auto sear), removing the disconnector gives you one shot, then the hammer down on a live round.  The AR-15/M16 needs super-soft primers or a dangerously long out of spec firing pin to slam-fire.