Document ID: ./input/supremecourt_opinions/opinions/23pdf/22-976_e29g.pdf
Page Number: 15

Cite as:  602 U. S. ____ (2024) 

11 

Opinion of the Court 

that  position  for  as  long  as  the  shooter  holds  the  trigger 
back, thus preventing the firearm from firing another shot.4  
Ibid. 

Figure 6. 

Finally, when the shooter takes pressure off the trigger and 
allows it to move forward (as indicated by the arrow), the 
hammer slips off the disconnector just as the square point 
of  the trigger rises  into  the  notch  on the  hammer (circled 
above).  Ibid.  The trigger mechanism is thereby reset to the 
original position shown in Figure 1.  A semiautomatic rifle 
must complete this cycle for each shot fired.5 
  ATF does not dispute that this complete process is what 
constitutes a “single function of the trigger.”  A shooter may 
fire the weapon again after the trigger has reset, but only 

—————— 

4

 Machinegun variants of the AR–15 style rifle include an additional 
component known as an auto sear.  The auto sear catches the hammer 
as it swings backwards, but will release it again once a new cartridge is 
loaded if the trigger is being held back.  P. Sweeney, 1 The Gun Digest 
Book of the AR–15, p. 38 (2005).  An auto sear thus permits a shooter to 
fire multiple shots while engaging the trigger only once.  ATF has accord-
ingly recognized that modifying a semiautomatic rifle or handgun with 
an auto sear converts it into a machinegun.  See ATF Ruling 81–4. 

5

 An animated graphic that displays the relevant movements is avail-

able at https://www.supremecourt.gov/media/images/AR-15.gif .