Firearms and barrel assemblies are provided herein that include a barrel assembly having a barrel having a proximal end and a distal end comprising a muzzle. The barrel also includes a chamber defined in the proximal end. The chamber includes a distal end and a proximal end. A bore extends distally from the distal end of the chamber. The bore defines a central axis of the barrel assembly. The barrel assembly also includes a barrel extension extending from the proximal end of the barrel. The barrel extension has a distal end and a proximal end. The barrel extension defines a bolt receiving recess in communication with the chamber. The barrel extension further has a barrel vent channel defined therein in communication with the bolt receiving recess. The barrel vent channel is defined in the barrel extension in a direction that is transverse to the central axis of the barrel assembly.