I have read that an AR15 can be built with a 12" bbl IF it has an extended 16" handguard that is attached to the barrel, thus becoming a "barrel extension".

Guess that the two need to be put together in some way that cannot be dissassembled.

Anyone done it ?

Tips, methods, tools etc ?

Thanks !

I think you may be thinking of the overall length for a vfg?

My 300 B/O TACSOL upper (a bottom) is made this way. Can fits inside UHG so OAL is the same as AR15 w/17" bbl.

The 12" 223 upper I bought has a threaded UHG that comes right off. In looking at various ones, I'm almost sure the one on it is from Monstrum

Monstrum sells an 16.5'" that will go right on. It's ordered.

Then comes the hairy part. ATF says any muzzle extension has to be pinned and welded/silver soldered to the bbl.

The bbl is steel, all the parts to mount the UHG and the UHG are aluminum. There seems to be a way to do it using TIG techniques.

Gonna t/w my class 3 dealer tomorrow as he has "contacts".

Guess my intent was not clear.

As with the TACSOL upper, the goal is to end up with a non NFA rifle that WITH THE CAN INSTALLED (REMOVABLE) IS almost as short as an AR with a 16" bbl.

The AR15 shown with the TACSOL upper and GEMTECH ONE works out to 17.5" to the end of the can.

So how to DIY it ?

Well I figgered it out.

"The ATF requires that all flash hiders, to be counted as part of the overall barrel length, must be pinned and welded or brazed on in a permanent fashion. No using Loc-Tite or just a wrench — the flash hider must be permanent!”

Same story for a barrel extension so——-

If everything is pinned and the pins welded over, this demonstrates it cannot be dissembled.

So my plan is to pin the Barrel nut to the barrel and aluminum weld the pins to the nut.

THEN put on the hand guard (barrel extension ) pin it to the barrel nut and aluminum weld the pins to the extension.

That way there is no need to weld steel to Aluminum.

I found an aluminum welding kit on Amazon that works with a MAPP gas torch.

The only way to get it apart will be to drill out the pins, so it will pass the ATF sniff test.

Where did you read that?
ATF has said that any muzzle device that is permanently attached can count toward the minimum 16" barrel length.
A handguard is not part of the barrel, even if permanently attached. (and neither is a bayonet welded to the barrel)

It will be permanently attached to the barrel. It doesn't have to be at the end of the barrel, it just needs to be permanently attached to the barrel and have the bullet going through it..

It will be so as the hand guard, barrel nut and barrel will all be one unit. Nothing can be disconnected from another without destructive intervention. (as with the TACSOL)

In the TACSOL as with my idea the bullet travels through the extension which is does not with any welded on bayonet.

The intent of the requlation is to prevent some bad guy having an easily concealable rifled long gun. My design is less concealable than a bone stock AR15.

If you can find a reg or case law that contradicts my idea, please share.

You wrote:"I have read that an AR15 can be built with a 12" bbl IF it has an extended 16" handguard that is attached to the barrel, thus becoming a "barrel extension"...That's why I asked "Where did you read that? "

Nothing from ATF seems to suggest anything of the sort. And they are the ones to determine whether your handguard counts toward the OAL of the bbl.

OP are you referring to something like this:



https://taccom3g.com/product/taccom-ar15-ulw-9mm-pcc-barrel/

Yes that is essentially what I envision. The difference being that rather than the extension butting up against the barrel nut, it will override it.

The extension/barrel nut and barrel will all be pinned/welded together creating a unit that cannot be taken apart without destroying it.

As for ATF, they have approved the TACSOL upper as NOT being an SBR. Both it and my idea have a welded/pinned barrel extension through which the bullet travels.

So what's the problem ? NIH ?

Be sure to fit the nut and barrel to the receiver first, if the nut is the type with a hole aligned for the gas tube.  Maybe you have the small diameter nut that doesn't need this.
Unless you just never plan on removing the assembly, will assume you have slots/openings in the HG to attach/remove the gas block,  or at least to remove the gas tube for replacement, if needed.
Then, after fitting the handguard for correct orientation, you could pin all together with one drilling operation; no need to do two separate pinning operations.
Unless you are using a direct thread only can, you might also consider first pinning the suppressor mount to the barrel.

Good thoughts.

Interesting when I click on my thread list, none show any responses ???

You're correct in that I can pin & weld in one operation as the TACSOL 9mm assembly shows.

As far as removing the gas block & tube, the Monstrum HG has lots of holes in it to access those parts.



And more could be added is necessary as it's still a barrel extension.

Just waiting for supplies to complete.

If I understand correctly, you want to have something like this without a tax stamp.

Attached File


I have a couple of SBRs set up with long handguards where the suppressor is under the handguard like you are talking about.

My question is what do you plan to do if you try to remove the suppressor and the tube unscrews from the endcap instead of the endcap unscrewing from the barrel?

I've had this happen a couple of times when I have gone too long without taking the suppressor off and cleaning everything. I had to remove the handguard tube in order to get a spanner wrench on the endcap.

ETA:  I think I would just build a pistol and put a brace on it.

The handguard will not be removable without drilling out pins and grinding off welds.

My can are all mounted using the GEMTECH quick mount. It mounts on the bbl and the can slips over ir and is locked on with a push and 180 degree turn. Impossible to get locked on. Even if it did 1.5" of the can is beyond the HG to use exreme measures to remove.

Look at the pic of my 300 B/O to see how it will look.

Finally got all the pieces and parts to assemble it.

Here are some pics.

1. shows the barrel extension pinned and welded to the barrel nut and barrel.

The rear attachment is the allen head that locks the handguard to the nut. It was drilled into and welded in place. The forward hole is a 8-32 screw that is D&T thru the handguard, barrel nut and slightly into the barrel. Then welded in place. This cannot be taken apart without drilling and cutting.

2. Shows it touched up.

3. Shows it assembled to the LWRC lower (with the GEMTECH ONE can in place) with the TACSOL 300 B/O upper above it.

Took to range Sunday. It worked perfectly.

I see now TACSOL is making a 223 version as well.

Mine cost 1/2 as much.

Do you have an ar pistol or sbr?  If not, you made an illegal sbr, even if only for a moment. The way that you made that, you had in your possession an assembled upper with a barrel less than 16”.  It may be gtg once welded, but for a while it was a not okay. The way that pinned and welded barrels work is that they are bought that way. If you buy a 14.5” barrel and diy your own pinning it could be constructive intent until it’s welded. I don’t see the .gov really getting that picky, but they could if they wanted to.

I’m not trying to start an ugly conversation.  I just want people to think about the dangers of having a short barrel with no legal home for it, even for a little while. If the feds raid your house and you have only rifles, but a short barrel, you’ve screwed.

I suppose you have a point IF the ATF were monitering the sale of every AR short barrel and short barrel upper and then kicking down doors to see if buyer had a lower within reach.

Being paranoid, I did all my assembly work far, far away from any lower, so had my door been kicked down, all they would have found is a "pistol" upper and some parts. Hardly illegal in my free state. To prove constructive intent, one would need a lower to "construct to".

Given the state of affairs in our country, I'd posit that folks are buying "pistol" uppers and squirlling them away just in case.

An unsuppressed 16" barrel is bad enough blast wise, can't imagine a shorter one.