Why Headspace is Critical
by Randall Davis
Fur-Fish-Game
August 2022 issue
Headspace is the distance from the face of a locked bolt or breech to the part of the chamber that limits how deep the bullet can be inserted. With rimmed cases, the rim stops the cartridge from being inserted deeper, and the thickness of the rim determines the headspace. Rimless necked cases stop where the shoulder of the case cannot go deeper; belted magnums stop on the belt. Headspace in a straight-wall rimless cartridge is from the bolt to the mouth of the case. Headspace matters because cartridge ignition releases explosive pressure, which pushes the brass casing out and forward. Properly supported, the case expands into the chamber will no ill effect. Too much space can cause a variety of problems, including a light primer strike that doesn't fire the cartridge. More concerning is a bulged/blown case separation, a split case shoulder or a primer unseated after firing. These can release hot gases that blow back around the bolt into the shooter's face. Checking the rifle's chamber with a headspace gauge (like the Go/No Go) and proper case re-sizing are critical.
