Hello all. I bought a used ar pistol off an individual.  Not sure if it was built as a pistol or converted from a rifle. Should I be concerned?  The overall length is 29 inches. It is s bushmaster lower with a custom built upper.

If you didn't know, and were concerned, why did you buy it?

Didn't say I was. Asked if I should be.  To many tricks with the atf. Just trying to be legit.

Well ATF says a rifle can never be converted to a pistol. But I don't know how you could confirm how the lower was originally configured. Did your bill of sale show it as a pistol to you? I think that's about all you can go on.

Bushmaster has sold stripped lowers in the past, and even now you can pick one up at Brownell's and elsewhere.  

However, the history of your particular lower is unknown.

If you want to be concerned, you can write Bushmaster a letter inquiring about how the lower left the factory.

Might can confirm with a phone call. They'd tell ATF with one, dunno if they will you.

For sure though, if Bushie released that lower configured as a rifle, using it for a pistol config is unlawful, however slight the chances you might get stung for it.

- OS

I would think you could call Bushmaster and they can tell you whether is was sold as a rifle completed from the factory or stripped. Or buy a Anderson lower $50 transfer the parts to be safe, use the Bushmaster for a rifle build.

Relax and enjoy your new pistol. The ATF is not coming to inspect in what configuration your lower left the factory. If you legally bought the weapon as a pistol you have absolutely no criminal intent or negligence. The ATF is not the Big Bad Wolf that many law abiding gun owners make them out to be.

But if you are concerned about the issue the suggestion above of buying a new stripped lower and switching the parts just to be safe would be a good way to ease your worries.

I appreciate all yalls input. I will enjoy it for what it is. Bushmaster told me it was built in 2006 but didn't say how it left the factory.  It's a great ar pistol.

The ATF never comes out on it's own. There are however thousands of different scenarios that they would be called out.
How about your neighbor call the police because he sees someone breaking into your house. Cops come, finds the pistol either with the suspect or in your house, calls to check just because thats what they do.
Girlfriend is pissed at you and calls the cops saying you hit her, cops come out, see above.
Many more possibles. Too many. Good news is if you did not know it was a firearm that needed to be registered , as in the OPs case (keep the receipt), you will not be prosecuted(Staples v. U.S.). But the firearm will be confiscated.