Muzzle
The forward end of the barrel, the opening the bullet exits through. Its surface is the crown, and it is often threaded for brakes or suppressors.
The muzzle’s surface is the crown. Many precision rifles thread the muzzle for accessories: muzzle brakes, suppressors, flash hiders, or thread protectors. Standard thread pitches are 5/8-24 for most US rifles and M14×1 for .338 Lapua.
Where the muzzle sits in space when the round fires is what defines the rifle’s pointing direction. Every other adjustment ultimately aligns to where the muzzle ends up at trigger break.