The AR-15 is the most popular long gun in American history. From the original full-length rifle to the shorter M4 carbine, it has been America’s “go-to” long gun for many years. But it isn’t just the original models that are popular. It is the short- and even ultra-short-barreled ARs in the form of the “modern pistol” or the short-barreled rifle (SBR) that have risen to the top of must-have lists. They are so much alike, what’s the difference?

Short-Barreled Rifles According to the Law

Let’s start by defining the primary term and regulations that control the arms in question. For that, we turn to the BATFE.


“Short-Barreled Rifle: A Rifle having one or more barrels less than 16 inches in length, and any weapon made from a Rifle, whether by alteration, modification or otherwise, if such weapon, as modified, has an overall length of less than 26 inches.”

Pretty straightforward right? A short-barreled rifle can be best thought of as a 16-inch-barreled, M4-style AR-15 carbine with a collapsible stock and a barrel cut down to less than 16 inches. SBRs generally have barrel lengths that run from 11 inches or less to 14 inches. Further, an SBR’s lower receiver must have started out life as a rifle lower — not a pistol lower — in order to be considered a rifle. This is true even though both lower receivers are exactly the same.

SBRs require a federal government “tax stamp” and the appropriate paperwork to purchase or build. The paperwork that BATFE requires for you to take possession of said short-barreled rifle could take upward of a year to process. There are two different forms used to obtain the tax stamp: ATF Form 1 for building your own SBR and Form 4 for purchases or transfers. has more information on the process—including estimated wait times.

The federal tax stamp is a form of firearms registration, which is also required for suppressors and full-auto arms. You can’t just get the stamp and apply it to different guns. It is an important piece of paperwork to keep with each SBR you may own. Because of these legal requirements, you also can’t just sell your short-barreled rifle to your buddy.

AR-15 Pistols

In “Pistol Braces: What Are They and Are They Legal?”, I discussed the basics of pistol braces and some of the possible pitfalls in building your own AR-15 pistol. The March 2017 Reversal Letter explained in the post caused an explosion in the popularity of pistol-brace-equipped AR-15 pistols because they were just as compact as an SBR (if not more so) with no tax stamp required.

The reversal collapsed the SBR market almost overnight. During a visit to my favorite gun store in Columbus, a security firm brought several high-end SBRs in for a trade. The sales rep I was talking with explained they wouldn’t be able to give them near the amount of money the rifles were worth. There just wasn’t as much of a demand for them since modern pistols could be had immediately with less hassle.

Here’s the Deal

Things are up in the air again. Sadly, the current administration is adamantly anti-gun. One of the multitude of efforts they are making against gun owners is to have BATFE re-classify the pistol-brace-equipped modern handguns as SBRs. This would mean SBR registration of some type would be necessary to possess such firearms legally.

Both short-barreled rifles and pistol-braced modern handguns are excellent weapons for tight space maneuvering. And they’re very similar when it boils down to it. For now, there is much less hassle in purchasing an AR-15.

*On Jan. 13, 2023, the BATFE amended its regulation on pistol braces. Gun owners will be required to register their stabilizing braces with the BATFE, permanently remove, dispose of or alter the stabilizing brace so that it can’t be reattached, or surrender modified guns to their local BATFE office.

Stay up to date with the ATF’s pistol brace and AR rules with this article.