'Bump Stocks' Before the Supreme Court
Here's why the Court should strike down the BATFE's 'bump stock' rule.
In 2018, the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) used its regulatory authority relative to federal firearm laws to rule that a bump stock is a “machinegun” as defined by the National Firearms Act (NFA) of 1934.
In relevant part, the NFA (26 USC 5845(b)) defines “machinegun” as a “weapon which shoots . . . automatically more than one shot . . . by a single function of the trigger” and “any part designed solely and exclusively . . . for use in converting a weapon into a machinegun.” The Gun Control Act (GCA) of 1968 (in 18 USC 921(a)(24)) adopted the NFA’s definition.
The NFA requires that to acquire a “machinegun,” a private individual pass a background check and pay a $200 tax to the IRS.
In 1986, an amendment to the GCA (18 USC 921(o)) prohibited new “machineguns” under the NFA regime. Thus BATFE’s rule means that owners of bump stocks—all of which have been made since 1986—would possess contraband and be subject to severe criminal penalties.
Michael Cargill, of Texas, sued. Last year, in Cargill v. Garland, the U.S. Court of Appeals for the Fifth Circuit ruled for Cargill. The court noted, “When ATF first considered the type of bump stocks at issue here, it understood that they were not machineguns. ATF maintained this position for over a decade, issuing many interpretation letters to that effect to members of the public.”
The court added, “A plain reading of the statutory language, paired with close consideration of the mechanics of a semi-automatic firearm, reveals that a bump stock is excluded from the technical definition of ‘machinegun’ set forth in the Gun Control Act and National Firearms Act.”
The Biden administration appealed. On February 28, the Supreme Court heard oral arguments in Garland v. Cargill. The arguments can be heard here and their transcript can be read here.
Where It Started
At least one bump stock was reportedly used, attached to a semi-automatic AR-15 rifle, in the mass shooting in Las Vegas in 2017. Thereafter, the usual suspects in anti-gun activism, political, and media circles said the devices should be banned.
However, the question before the Court in Cargill is not whether bump stocks should be banned. It is whether a bump stock causes a semi-automatic rifle to fire “automatically more than one shot . . . by a single function of the trigger.”
As the following explanation shows, is it mechanically impossible for a semi-automatic rifle to fire “automatically” or to “fire more than one shot by a single function of the trigger.” This is because some of a semi-automatic rifle’s parts are designed to make it mechanically impossible. In the case of an AR-15, there are five such parts (plus a sixth that is not relevant), and one of the five parts prevents the installation of another part that is required for automatic firing.
Automatic vs. Semi-Automatic Firing
The AR-15 is identical to the M16, from which it is derived, except that, for three reasons (explained below), whereas an AR-15 can fire only semi-automatically, an M16 can fire semi-automatically or automatically, the user selecting between the two modes of operation by adjusting the position of the selector (a lever on the side of the rifle).
This is an AR-15 with its selector set to semi-automatic. Note that the selector is vertical. (The rifle’s manufacturer markings and serial number are covered by the white boxes.)
This is an M16 with its selector on semi-automatic. (As with the AR-15, the selector is vertical.)
This is the M16 with its selector set to automatic. Now, the selector is horizontal.
As noted, there are three reasons why an AR-15 cannot fire “automatically” (i.e., “more than one shot by a single function of the trigger”).
First, an AR-15’s trigger, hammer, disconnector, and selector are different from those of an M16. Here are the M16 and AR-15 triggers, hammers, disconnectors, and selectors, with the M16 ones on the left in each photo. The triggers, viewed from the rear, . . .
. . . hammers, . . .
. . . disconnectors, . . .
. . . and selectors.
Second, an AR-15 doesn’t have an M16 “automatic sear.” Third, an AR-15’s “receiver” (the part of the rifle that holds the trigger, hammer, disconnector, and selector) is made narrower internally than that of an M16, to prevent the installation of an automatic sear.
Here is an M16 receiver on the left, with the automatic sear circled, and an AR-15 receiver on the right. Notice that the AR-15 is narrower internally, to prevent the installation of an automatic sear.
Now, let’s go through the M16’s eight-step automatic firing cycle of operation. To begin, the hammer must be cocked.
The hammer is prevented from flying forward to fire the rifle by the “sear” (not to be confused with the “automatic sear,” mentioned previously). The “sear” is the top, front edge of the trigger, . . .
. . . which engages a groove in the bottom of the hammer.
Outside the rifle, the sear, engaged in the groove in the bottom of the hammer, would look like this:
Inside the rifle, though you can’t see the underside of the hammer where it’s engaged by the sear, it looks like this:
Now, the eight-step automatic firing cycle of the M16 can begin.
1. Firing. The user pulls the trigger, which disengages the sear from the groove in the bottom of the hammer. The hammer flies forward and strikes the firing pin, which strikes the round of ammunition in the chamber (the rearmost portion of the barrel), firing the rifle.
2. Unlocking. The bolt-carrier assembly moves rearward. The bolt rotates and unlocks from the barrel extension.
3. Extraction. The extractor (within the bolt, within the bolt-carrier assembly) pulls the fired cartridge case out of the chamber.
4. Ejection. The bolt’s ejector pushes the fired cartridge case out of the rifle.
5. Cocking. As the bolt-carrier assembly continues rearward, it cocks the hammer, and the automatic sear locks the hammer in the cocked position, as shown in the following photo.
6. Feeding. The bolt-carrier assembly returns forward and pushes a new round of ammunition toward the chamber.
7. Chambering. The bolt-carrier assembly continues forward, pushing the round of ammunition into the chamber.
8. Locking. The bolt locks into the barrel extension and the bolt-carrier assembly hits the automatic sear, causing it to release the hammer. The hammer flies forward, and the rifle fires again.
As long as the trigger is held to the rear, the rifle continues firing through the cycle by itself . . . that is, automatically. When the user releases the trigger, the sear rises and engages the groove in the bottom of the hammer (as shown in photos #s 10-13), preventing the rifle from firing again.
Semi-Automatic Firing
An AR-15’s (or M16’s) semi-automatic cycle of operation differs from an M16’s automatic cycle in two respects.
In step #5: Whereas in automatic firing the “automatic sear” locks the hammer in the cocked position (shown above, photo #14), in semi-automatic firing the disconnector locks the hammer. Outside the rifle, the disconnector lock upon the hammer looks like this:
Inside the rifle, it looks like this:
In step #8: Whereas in automatic firing the automatic sear releases the hammer, allowing it to fly forward to fire the rifle, in semi-automatic firing the disconnector, which locked the hammer in the cocked position in step #5, continues to do so, preventing the rifle from firing.
To fire the rifle again, the user must do two things. First, he or she must release the trigger, to disengage the disconnector from the hammer. (This “resets” the trigger.) When the trigger is released, the hammer goes forward a short distance, where it gets locked in the cocked position by the sear, as described and shown in photos #s 10-13.
Second, he or she must pull the trigger again. Hence, 18 USC 921(a)(29) defines “semiautomatic rifle” as “any repeating rifle . . . which requires a separate pull of the trigger to fire each cartridge.”
In conclusion, because the AR-15’s trigger, hammer, disconnector, selector, and receiver are designed to prevent the rifle from firing automatically, and because an AR-15 does not have (and its receiver cannot be fitted with) an M16 automatic sear, it is mechanically impossible for an AR-15, with or without a bump stock, to fire “automatically.”
Furthermore, because performing the “single function” of pulling the trigger and firing the rifle causes the AR-15’s disconnector to thereafter lock the hammer in the cocked position, preventing the rifle from firing again until the trigger is released (reset) and pulled again, it is mechanically impossible for an AR-15, with or without a bump stock, to fire “more than one shot . . . by a single function of the trigger.”
© Mark Overstreet, 2024