ATF Decides a .50 BMG AR-15 Upper is a… Firearm?
Thanks to the arrival of our second child and all the hoopla over 3D printed guns that has dominated airwaves the past week or so, I’m a bit behind in covering this topic. Because of that, I’d recommend readers (who haven’t already done so) to check out The Firearm Blog’s article on the issue as well as this one I am sharing here.
In short, a foreign manufacturer of unknown identity recently submitted a bolt-action, .50 BMG AR-15 upper assembly to the ATF for import approval. After examining the upper, the ATF classified it as a firearm receiver. Thus, subjecting it to all the additional regulations that category involves (FFLs, background checks, etc.). The move, which is a departure from the ATF’s standard practice of treating assembled AR-15 uppers as mere parts, led the agency to write other manufacturers informing them of the change and instructing them to treat their products accordingly. Safety Harbor Firearms is a manufacturer of similar .50 BMG upper receiver assemblies and was the first to notify TFB of the ATF’s letter. Since then, other companies have confirmed that they too received the notice.
But Why?
This change understandably has some gun owners worried that the ATF may choose to treat all AR uppers as firearm receivers. Though the fear is understandable, there’s a lot to unpack here before we jump to conclusions.
In the Safety Harbor letter shared above, the ATF makes a somewhat cloudy distinction between bolt-action firearms (and uppers) and their semi-automatic counterparts. According to the agency, it has traditionally held that the portion of a bolt-action firearm to which the barrel attaches and which houses the bolt constitutes the receiver for legal purposes.
What the agency does not describe is their rationale for treating a semi-automatic upper receiver differently. This means that in order to gauge the impact of this new ruling, some assumptions must be made. Please be aware that this is not a defense of the ATF’s decision. It’s simply an attempt to understand where they’re coming from and how far this conclusion could reach.
Looking at bolt-action uppers, and .50 BMG models more specifically, there are a few operational details that set them apart from their semi-auto brothers. First, they’re breach loaded, which renders the lower’s magazine well vestigial. Second, the bolt manually locks into the barrel/barrel extension. Ergonomic difficulties aside, a bolt-action upper is theoretically usable without a lower receiver. The buffer assembly isn’t needed and more importantly, the bolt won’t fly out the back of the upper receiver after a round is discharged. Therefore, in the case of .50 caliber upper assemblies, the AR-15 lower receiver is little more than a trigger pack.
In contrast, a semi-automatic AR-15 relies far more heavily on the function of the lower receiver. The lower houses the magazine well that’s responsible for ammunition feeding, the trigger assembly for firing, and the buffer assembly for reliable and safe bolt/carrier operation. If you try to use a standard AR-15 upper as a standalone firearm, you’ll be limited to single-shot operation. And if you do manage to touch-off a chambered round, you’ll also have to dodge the bolt carrier as it launches out the back of the receiver. In short, the upper is useless without a proper lower receiver.
Other Examples
The move’s effect on other types of upper receiver groups is not clear. Will pump-action and other bolt-action receivers get the same treatment? We can’t say. However, the end of the letter notes that “ATF has previously determined that non-standard AR-type upper assemblies, when attached to an AR-type receiver, does not preclude the upper assembly from being classified as a firearm ‘receiver’.”
The precedent that TFB seems to have missed is likely BRP Corp’s XMG upper. The XMG is an MG-34 lookalike upper assembly designed to mate with an AR-15 lower. It is exclusively belt fed and sports its own buffer assembly. Its classification as a firearm receiver means that most XMG owners are forbidden from (legally) using them on registered full-auto lowers. In contrast, Fightlite’s also-belt-fed MCR upper assembly uses the original AR-15 buffer tube and can still be fed through the original magazine well. It is not a firearm receiver by ATF standards. At the same time, the AR57 upper feeds from a top-mounted FN P90 magazine yet it is not a firearm receiver according to the ATF, likely due to the preservation of the buffer assembly that attaches to the lower receiver.
Based on this precedent and the decision regarding .50 BMG uppers, it seems that upper assemblies that render both the lower’s magazine well and buffer assembly unnecessary might find themselves classified as firearm receivers. Again, this is an assumption grounded in limited evidence, but the ATF appears somewhat consistent here. Most importantly, it does not appear that the agency has any plans to treat standard AR-15 upper assemblies as firearm receivers any time soon.
An information security professional by day and gun blogger by night, Nathan started his firearms journey at 16 years old as a collector of C&R rifles. These days, you’re likely to find him shooting something a bit more modern – and usually equipped with a suppressor – but his passion for firearms with military heritage has never waned. Over the last five years, Nathan has written about a variety of firearms topics, including Second Amendment politics and gun and gear reviews. When he isn’t shooting or writing, Nathan nerds out over computers, 3D printing, and Star Wars.