I would like to build a brand new lower with a LAW tactical folding brace. If I put a Magpul on the buffer tube/brace, is the LOP still restricted to 13.5?Can this be done in ATF compliance?

Am I further ahead to build the folding lower, and then use a 14.5in barrel with a flash hider? This would give a 16 oal barrel.

I do not want ATF trouble.

Thanks.

By Magpul, I assume you mean a shoulder stock?
A ''shoulder stock'' does not have any max LOP requirement.
An ''arm brace'' should not exceed 13.5'' LOP.
A barrel less than 16'' must not be used with a shoulder stock unless you pay a $200 tax to make a short barrel rifle. A barrel less than 16'' can be used to make a ''pistol'' and an arm brace is fine on a pistol.
A 14.5'' barrel with a permanently attached muzzle device that turns the barrel into a full 16'' can be used with a shoulder stock to make a rifle.

You might want to do a bit more homework before you start connecting uppers and other things to your lower.

Assuming you want to build a pistol, since this is posted in the pistol section of the forum:
Start with a pistol or "virgin" lower receiver.
You can only use a brace on your buffer tube, no magpul stocks. A stock changes the pistol into a short barreled rifle.
With a lot of braces that would be compatible with a LAW folder, I'm finding that it increases the length of pull to more than 13.5". You'll want to get some details on the specific braces that you're interested in before adding the LAW folder to the equation.

Your question about the 14.5" barrel with a flash hider: Basically to achieve a barrel length of 16" that flash hider must be pinned and welded if you are going to include it in your measurement. Otherwise it doesn't count as part of the length.

Hope this helps.

I forgot to mention that if you put a shoulder stock on that lower, if you choose to pin a weld a flash hider to a 14.5" barrel to configure a rifle, you will have created a rifle from that lower, and once that is done the lower can never be reconfigured as a pistol at any point in the future.

I believe the above is incorrect.  A pistol may be converted to a rifle and be converted back to a pistol.  But, if a lower is built first as a rifle, it is always a rifle and cannot be built as a pistol.

Always this.

You are incorrect...a pistol lower can be made into a rifle and back into a pistol at anytime...a rifle lower cannot be made into a pistol...ever...unless you SBR it...but than it is not a pistol anymore.

Do you want a 14.5" barrel pistol? Is that what you're saying?

If you put a stock on it, it isn't a pistol. If you pin and weld a flash hider to make the barrel 16" OAL you have no reason for a pistol brace.

Some interesting disinformation floating around this thread.

The only thing that makes a lower a "pistol" lower is for it to have been assembled as a pistol.  You can buy a lower advertised and marked as a pistol lower complete with extension and brace.  If the first thing you do is put a stock  and  rifle upper on it, before completing a pistol assembly, it is now and forever more a rifle lower.  You can not legally make a pistol using this lower.

If you buy a rifle lower complete with extension and stock and the first thing you do is put a brace and pistol upper on it, it is a pistol lower.  You can make this lower into a rifle and back to a pistol by changing out the rifle and pistol parts.

This is all true regardless of any markings on the lower, the advertising, what a dealer incorrectly put on the 4473,...  The first configuration of the weapon, rifle vs. pistol, determines what the lower is in the eyes of the ATF.

THAT, exactly what I was referring to. The whole point of a "virgin" lower for pistol builds...

A ''pistol'' is defined by being originally designed, made and intended to be fired with one hand. This is why building a pistol from a receiver that was originally a different firearm, such as a rifle, is a problem. A pistol can not be ''originally'' a pistol if it was previously made into something else. Rules and recommendations sometimes make more sense if you know the point behind them.