Final answer:
The firing mechanism in a modern firearm, such as the firing pin and trigger, serves the same function as the lock on a muzzleloader.
Step-by-step explanation:
In a modern firearm, the part that serves the same function as the lock on a muzzleloader is the firing mechanism. The lock on a muzzleloader is responsible for igniting the gunpowder and propelling the bullet forward, and the firing mechanism in a modern firearm performs a similar function.
The firing mechanism in a modern firearm typically consists of several components, including a firing pin and a trigger. When the trigger is pulled, it releases the firing pin, which strikes the primer, igniting the powder and firing the bullet.
So, just like the lock on a muzzleloader, the firing mechanism in a modern firearm is responsible for initiating the firing process.