If I understand correctly, muzzle devices like a flash hider, flash can, etc DO count toward barrel length as long as they are permanently attached. With that said, is there a reason one would need to be able to remove them (cleaning or something?) or would it be ok to permanently attach one? For example, a 12.5” barrel with a permanently attached 4” flash can would legally meet the requirement for a non-sbr barrel, but would you ever need to be able to remove it?

Don't know about a flash can, but I have a 5.5" flash hider pinned and welded on a 9 mm upper and I clean it the same as cleaning the chamber/barrel. Even on removable flash hiders, the only time I have taken one off was when I was going to replace it with something different.

So no, I don't think you would "need" to remove it and would be fine with it permanently attached if needed to be legal.

I believe flash can has the same criteria as a flash hider or any other muzzle device. As long as it’s unremovable (pinned&welded), it will count as the overall length of the barrel. If it’s removable (just screwed on with locktite), then it does not count towards the barrels overall length.

With that being said, I don’t foresee a need to ever remove a flashhider, flashcan or any other muzzle device other than an actual suppressor (mainly a .22lr one). Any cleaning you want to do to a muzzle device can always easily be done with it attached.

Yes

The only reason to be able to remove it would be to change out the gas block and handguard.
If you are happy with the set up and will NEVER want/need to change those, then no. There is no need to be able to remove it.

You are correct. If it is pinned and welded it's considered in the OAL of the barrel.

If you ever remove a pinned and welded barrel attachment from a firearm that is not registered with the NFA and has a barrel less than 16" then you will instantly be in posession of an SBR while it is off. That is why they are permanent. Silly as heck, but that's the law as it was explained to me.

I mean, that kind of makes sense. You’re in possession of a functional rifle with a barrel less than the 16”. It’s not different than chopping a barrel of a 18” down to 10”. It changes the classification of that rifle.

Plot twist: just put a pistol brace on it (while they are still legal).

Second plot twist....that is in no way, shape, or form legal if the lower was originally designated as a rifle..

From a legal standpoint, by removing the pinned and welded attachment, you have turned a legal rifle into an illegal SBR. You can't turn an SBR into a pistol by putting a brace on it b/c the weapon was originally designed as a rifle. Instead, you have simply turned your NFA SBR (which it became the instant the attachment was removed) into a "weapon made from a rifle," which is still regulated by the NFA.

Hard and fast rule...if a lower was originally designated as a rifle, it will always be a rifle in your possession in the eyes of the NFA....unless you apply for a SBR tax stamp (in which case it's still a "rifle").

I have one that is permanent, however the OD of the flash hider and barrel are the same so the gas block and handguard, etc. fits right over it. Works fine I can't tell any difference really even shooting in the dark next to a 16" barrel with a standard A2.

I’ve heard that before, but I really question how enforceable that is, if it’s even a thing. If you purchase a lower and put a sig brace with an 8” barrel, did you just build a rifle, or a pistol? If you then put that same lower on a 18” upper and a fixed stock with that same lower, did you convert a pistol into a rifle? What if you go back?

I can see going from a legit registered SBR to a pistol could possibly cause an issue because it’s technically an NFA registered weapon, but there’s no way anything other than that can be enforceable on an individual level.

If the 4473 lists the original purchase as a "rifle", it is both easily traceable and 100% enforceable.

Stripped lowers are mostly designated as "other" for this reason. They can be built as either rifle or pistol.

But, if you buy an AR15 rifle...it will be designated as a rifle on the 4473 and therefore will always be a rifle in the ATF's eyes. If that firearm somehow lands in their hands with a barrel shorter than 16" overall (including any PERMANTLY attached devices) without an SBR stamp, even with a pistol brace, someone is in A LOT of hot water with one of the worst outfits to be in trouble with.

Will the ATF go through all that trouble to run it down? Maybe, maybe not. But, the law is clear that a rifle cannot be converted to a pistol, and the punishment can be very severe.

I have tried every sort of muzzle device there is. I can't find any real use for one other than a muzzle brake and it's not needed until you get into the high powered stuff. Adds weight and doesn't pull it's weight. None of mine have any muzzle device. My .50 beowulf did and it worked.

Surefire Warden works pretty good till my SF can gets out of jail