I think it is understood that m16 parts in an ar15 are not legal.  
Is it legal to own m16 parts if NOT installed in a rifle?   or
Is it legal to use m16 parts in an ar15 if they have been modified?

Thanks for your input

You can use the M16 bolt and carrier, but you can not use or own any M16 FCG (fire control group ie:trigger components).

The BATFE doesn't like it when you have full auto parts and a weapon to put them in either (even if they're not in there currently).  It's called "intent" and they can pin it on you if they are already after you for some other infraction.

Quoted: You can use the M16 bolt and carrier, but you can not use or own any M16 FCG (fire control group ie:trigger components).

Yup.

Bolt/carrier is absolutely fine.

By the LETTER of the law, even SOME fire control parts would theoretically be okay, as long as it is not possible for the rifle to fire full-auto, but I would not chance it, since it get's closer to the "constructive intent" line.

But the full-auto carrier is fine in a semi-auto AR.

Welcome to ARFCOM!

Larger collar firing pin ok to?

A second consideration is in which State do you live.  Most States as well band the lower M16 trigger assemblies.  When in doubt, check with both the BATF and your State’s Attorney General’s Office and request copies of the Laws that affect you and your weapon.

I for one can’t afford the ammo that one would burn up!  However, I’m going to use a M16 Bolt Carrier on my Colt 7.62x39 AR to help with the recoil.  

ArticWolf

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Quoted: I think it is understood that m16 parts in an ar15 are not legal.   Is it legal to own m16 parts if NOT installed in a rifle?   or Is it legal to use m16 parts in an ar15 if they have been modified? Thanks for your input

Just having the parts nessescary to convert a SA to FA rifle is considered a machine gun.

theoretically, you should be able to run the m16 b/c & fcg. it's the auto sear or drop-in auto sear (dias) that constitute illegality w/o proper paperwork. the b/c & fcg alone will not turn an ar into a mg

that said, if the feds confiscate your m16 b/c fcg equiped weapon, they can remove/disable the disconnector to effect full auto tendencies. then you're screwed.

Quoted: Quoted: I think it is understood that m16 parts in an ar15 are not legal.   Is it legal to own m16 parts if NOT installed in a rifle?   or Is it legal to use m16 parts in an ar15 if they have been modified? Thanks for your input Just having the parts nessescary to convert a SA to FA rifle is considered a machine gun.

Not by the current BATF ruling.  In either case, what would you use beyond the bolt and bolt carrier?

Would there be any advantage or disadvantage to running the FA or SA bolt and carrier?

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Quoted: Not by the current BATF ruling.  In either case, what would you use beyond the bolt and bolt carrier?

A DIAS or M16/modified AR lower w/ auto sear (not just the FCG itself) would be required to convert a weapon to FA. Get caught by the ATF w/ one of those (that is unregistered), your ass is grass.

Quoted: Would there be any advantage or disadvantage to running the FA or SA bolt and carrier?

Alot of people prefer the FA b/bc due to it being a little heavier, it slightly increases the lock time. I prefer to run a FA b/bc.

OK. Roger on the full auto carrier; and just to cover all the bases, you can use most Full Auto parts IF (and it's a big if) you modify them to semi auto only configuration.

For instance, the select fire hammer has a tab at the top rear to engage the auto sear in FA fire.  If you gring off that tab, you now have a semi auto only hammer.

The FA disconnector has a tab at the rear that's depressed by a surface on the selector in full auto.  Grind off that tab and you now have a semi auto only disconnector.

The select fire trigger rear slot is cut all the way back to clear that disconnector tab, and if you drop a weld bead back there to close off the rear end of the slot you have a semi only trigger.

You can even modify a select fire selector to semi only, by grinding off the shoulder in the middle that depresses the disconnector, though that will still leave you w/a switch that clicks into the full auto position.  It'll just give you two semi auto fire positions.

In the old days of the late '60s, early '70s, when decent quality aftermarket parts were rare to nonexistent, a lot of us did the above with viet Nam era Colt M16 parts, to be able to use decent quality pieces in our ARs.  In this day and age, it's not really necessary any more, since you can now get top quality aftermarket pieces. On the other hand, when recently building up a civie version of the origiknal M16, using a Colt upper assy and original chrome bolt/carrier assy, I did exactly that

It was purely for getting the piece as authentic as possible. Fact is, I could have ordered the parts from Bushmaster, Rock River, or Stag, and gotten exactly the same quality stuff. They just wouldn't have had the "C" on 'em.