I know this has likely been asked a thousand times so I apologize in advance. Just too much conflicting info out there IMO

I have read so much conflicting info that my head is spinning now.

I am trying to do a build with a 10.5" barrel PSA upper. It will not be 26" or more OAL, obviously.

In order to legally have an adjustable buttstock, without the tax stamp, would I need to measure it with the stock extended or completely collapsed? If collapsed, then it clearly won't make the cut so I'd need to put a brace on it. If so, fine.

But are there any adjustable buttstocks, using your standard mil-spec buffer tube, on the market that would get me to the 26" OAL LEGALLY WITHOUT NEEDING THE TAX STAMP? If so, which? I would like to put a Magpul AFG on this thing.

OAL of at least 26 inches, AND your barrel needs to be at least 16 inches (not including the muzzle device if it is not permanently attached).

You need an upper with a 16" barrel (or 14.5"/7" pin and welded) if you want a stock.

If the barrel is less than 16" long you will need a stamp if you want to put a buttstock on it, regardless of overall length.  You can put a pistol brace on it for now but will still be under 26" OAL with a standard carbine tube.  There are pistol buffer tubes that are 9-1/4" long, rather than the normal 7-1/4", that will get you to 26" OAL with a 10.5" barrel.  You still can't put a stock on it without a stamp, but you could put a vertical foregrip on it if you want.

To be clear:

Barrel under 16", with, or without pinned device, brace or no brace ~

It is a PISTOL

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EXCEPT IF:

It has a rifle stock ~ SBR pay $200 to the man, or go to jail.

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It does not have a stock, but has a vertical (90*) foregrip, and is under 26" when made as small as possible in firing configuration ~ ANY OTHER WEAPON (AOW) pay the man $200, or go to jail.

NOTE: This very confusing law was written to go after gangsters in the Prohibition Era. Who were using Thompson SMGs and Semi Autos, with the stock removed, to do the first drive-by shootings.

Understand that, you understand the law.

Go look at a Tommy Gun with the stock off.
Don't try to make your AR15 look like it without paying the man $200.

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It does not have a rifle stock, but has a 90* vertical foregrip, and  is over 26" in the smallest firing configuration ~ FIREARM just another plain ol' gun, like a pistol, or a rifle.

OP, this is what you seek, with the exception that the ATF measures with the brace fully extended, IIRC last time I read a letter. It makes no sense, but little in that unconstitutional division ever does.

So, What about Franklin Armory XO-26?

That is considered a "firearm" just like the Mossberg Shockwave and similar guns.They were designed built at the factory WITHOUT a shoulder stock AND meant to be shot using two hands. They still must meet the 26" OAL rule. If they are shorter than 26" OA then they are an AOW. Put a shoulder stock on them and they are a SBR due to the barrel being under 16" OAL.

Another thing to remember with guns classified as a "firearm" with an OAL of at least 26" AND a barrel less than 16" (18" for shotguns) is that as soon as you conceal it in anyway it instantly becomes an AOW per federal law.

For any barrel under 16" OAL installed on a lower WITH a shoulder stock, you MUST use a muzzle device that brings the OAL to at  least 16" AND is permanently attached to the barrel.

A pistol can have any length of barrel per federal law and still be a pistol as long as there is no shoulder stock attached.

I know, clear as mud. But I hope this helps.

I can't remember off the top of my head, but you might want to check the ATF proposal on braces.    

I think they are going away with the ability to have a braced firearm, but I can't remember if they were re-writing all of those rules or not.

I have a 12.5" upper with a 90 degree VFG, and an SBA3 on a standard carbine buffer tube.  That is currently a firearm.  When I swap the 90 degree VFG for a handstop (or nothing), it is a pistol under federal law....but the AFT is trying to change all of that.

When measuring OAL to qualify for 26" minimum, they measure to the rear of the buffer tube with adjustable stocks.

Another thing to remember about converting a shockwave type firearm to an SBS.  It cannot go back to being a firearm.  That designation only applied to them because they never had a stock begin with.

I may be mis-remembering, but I think that's their short barrel model that has a butt stock. They had special barrels made with no rifling so they could claim they're other firearms.

A tax stamp for an AOW is only $5. SBR and SBS are $200 tax stamps.

I'm not sure who you are replying to but to clarify if you are building an AOW it's still a $200 tax to make it and then a $5 stamp to transfer it. @AlexC3

I was responding to Bullet's post. I have never manufactured an AOW and was under the impression it was $5 for transfer and manufacture. I should have verified before replying, you guys are correct.

I think you may be confusing that >26" OAL allowance to be able to put a VFG on it, not a buttstock. You're never legally allowed to put a buttstock on a rifle barrel that's short than 16" unless you've registered it as an SBR.

Also, measurements must be taken from the end of the bare barrel with no muzzle device installed (unless it's pinned and welded on) and to the end of the receiver extension/buffer tube with no brace or stock on. And if you have a folding stock device then you have to measure to the the hinge.

So how’s it classified if it’s under 26”?

It is a pistol if the barrel is less than 16", unless it has a rifle stock then it is an SBR.  Under 26" pistol you can't have the vertical foregrip that you can if over 26".