I am attempting to ship a built ar15 lower to a guy in Texas from Texas. Now my question is when I bought the lower it was registered as a receiver. Will I get in hot water just shipping it straight to the guy? Thanks in advance for any help

Legally yes, you can ship a long-gun from a Texas resident to a Texas resident however you are going to likely meet ignorant postal workers if you declare the contents. I tried to ship a long gun from Texas to Texas and the USPS manager finally threatened to call the police (to which I said I would wait) and have me arrested. The police did come and while I was able to prove that I was within my right he said there was nothing he could do to force the post office to accept my parel.

432.1 General
The following conditions apply:
a. Pistols, revolvers, and other firearms capable of being concealed on the person (referred to as handguns) are nonmailable in the domestic mail except as permitted in Exhibit 432.1 and DMM C024.1.0.
b. The disassembled parts of a handgun or other type of nonmailable firearm that can be readily reassembled as a weapon are nonmailable except as permitted in Exhibit 432.1 and DMM C024.1.0 or C024.2.0.
c. Unloaded antique firearms sent as curios or museum pieces are generally permitted as specified in Exhibit 432.1 and DMM C024.2.0.
d. Unloaded rifles and shotguns may be mailed if the mailer fully complies with the Gun Control Act of 1968 (Public Law 90-618) and 18 U.S.C. 921. The mailer may be required to establish, by opening the parcel or by written certification, that the gun is unloaded and not excluded from mailing because of the restrictions in 431.2b and c.
432.2 PS Form 1508

My advice is to just save yourself the headache and find a local FFL to ship it for you, it's not worth your time to argue with the ignorant.

Thats what I was thinking,and the whole receiver thing has me questioning it

it's considered a long-rifle; you can ship it but again it's going to be an (unnecessary) hassle dealing with USPS. There are lots of FFL's that will ship it for you for the cost of shipping and probably an additional $15 or so. Your buyer will cover that.

Since its a lower it will be easy to box up inconspicuously and you are not required to tell them you are shipping a firearm, they will never know. Its much harder to fight with their ignorance azz when you go in there with a box or case that clearly SPELLS gun, though its perfectly legal and shouldn't be such a pain in the azz.

While a lower requires a background check, by itself it is incapable of firing a round thus is not yet a firearm?

The lower is the serial numbered part - it is considered a firearm with or without an upper. FTF in texas does not require a background check.

It's classified as a firearm and need to go through a ffl dealer when you purchase new. What I'm wanting to do is send it to a individual tx to tx which is legal but I can't find out if a lower is classified as a pistol since it's technically not a rifle

I thought you said it was built. With a stock attached isnt it a rifle now?

Yes it has a stock attached but was registered as a receiver. That's where the gray area is

It doesn't make a chit of difference if its in 1 piece or 3 pieces, Texas law allows you to sell firearms, private party to private party without an FFL, and its perfectly legal to mail a long gun through UPS or USPS to another Texas resident.

This.

Ya'll are complicating it too much.

A stripped lower or built lower is the same. It is the registered part with the serial number. Doesn't matter anyhow...ship it. Just not across state lines.

I've shipped Texas resident to Texas resident, but it is a real pain. You can only do it thru the post office, and if you don't tell them the package contains a firearm then you are in violation of federal law. Most of the postal employees don't know the law and like it is said previously it really isn't worth the hassle.