Can I purchase an AR receiver face to face from an adjoining state?  I would do a 4473 and abide by my state's waiting period etc.  i have looked at the ATF website and can't find an answer.  I'm sure this has been discussed ad nauseum, but can't find any definite answers.

Thanks, Will

Out-of-state face-to-face is not legal. Have the seller bring it or ship it to your dealer.

From ATF FAQs

A person not licensed under the GCA and not prohibited from acquiring firearms may purchase a firearm from an out-of-State source and obtain the firearm if an arrangement is made with a licensed dealer in the purchaser’s State of residence for the purchaser to obtain the firearm from the dealer.

[18 U.S.C. 922(a)(3) and 922(b)(3)]

I cannot purchase an AR receiver from a FFL dealer in an adjoining state?  I've bought long guns from neighboring states.  Do you know where i can find the ins and outs of this on the ATF website?

Ah, I saw face-to-face and assumed private sales.  But still, you cannot buy a receiver when visiting another state.

That is what I'm sensing, but cannot come up with a definite letter from the ATF about it.  Oh well, i guess my current AR pistol will have to work for now.

The reason is the law states your can purchase rifles or shotguns when visiting another state, but since a receiver is neither a rifle nor shotgun....  18 U.S.C. § 922 : US Code - Section 922: Unlawful acts

You can have the dealer in the other state ship it to a dealer in your state however.

I just thought building a new AR when on vacation next week would be fun, but I will have to wait until I get back.  Thanks for all of your input!

From a licensee in another state, not just purchase in general.  

Private face to face sales are only legal in your own state of residence, with another resident of your state.  All other transactions end up involving an FFL in one way or another.

I only know for Texas and Louisiana, but I cannot buy any gun other than a long gun in an adjoining state. A receiver is not a long gun. Pistols, pistol grip shot guns, and receivers would have to be sent to my FFL and visa versa.

In short, no.  If your state law allows it you can sell a long gun to out of state residents, but a stripped receiver has the ability to be classified as a pistol and therefore is treated as a handgun in terms of transfer (21, instate resident, etc.).  If you assemble it as a rifle or deem it a rifle then you're good to go, but that's an incidence of manufacture (07 or 10 and FET if over your 50/yr) and that rifle can never be a pistol.

Has nothing at all to do with "ability to be classified as a pistol".

Federal regulations governing FFLs prevent them from selling ANY firearms to any person under 21 years of age.  Be it a handgun, receiver, machinegun, sound suppressor, whatever.  There is then an exception which allows FFLs to transfer complete rifles and complete shotguns to persons over 18 years of age, and to residents of any state, provided the FFL's state and buyer's state laws permit it.  

THAT is the reason out of state buyers cannot purchase handguns or receivers or machineguns from a dealer outside their own state, not some imagined ability to be classified as a handgun.

Dealers or persons cannot "deem it a rifle" to allow an out of state purchaser to acquire one, whether the out of state purchaser is 18, 21, or 90...

Nailed it.