What part of a bolt-action rifle is responsible for sealing a cartridge into the chamber?

The bolt is the component of a bolt-action rifle that plays a crucial role in sealing a cartridge into the chamber. When the bolt is closed, it engages with the locking lugs on the receiver, creating a secure seal that prevents gases from escaping during firing. This ensures that the pressure generated by the ignited cartridge is contained within the chamber, allowing for the proper functioning of the firearm and enhancing the safety of the shooter.

Additionally, the bolt also facilitates the feeding of cartridges from the magazine into the chamber, as well as the extraction and ejection of spent casings after firing. Its design is integral not only to the sealing of the chamber but also to the overall cycling of the action in bolt-action rifles.

In contrast, other parts like the butt, which refers to the rear end of the stock, and the magazine, which holds cartridges but does not engage with the chamber itself, do not directly seal the cartridge. The safety, while an important feature for preventing accidental discharges, does not play a role in the sealing of the cartridge in the chamber during the firing process. Thus, the bolt is the correct answer as it is the only part specifically designed for this function.