![]() ![]() New cartridge cases can normally stretch a lot before breaking. If (and only if) the amount of head movement exceeds the elastic limits of the case, the cartridge separates into two pieces. The higher the pressure, the more they move.)ĥ. (In rear-locking actions like the Lee, the bolt and receiver also compress/stretch to add a little more movement. The solid case head can't expand and grip the chamber, so it moves rearward, re-seating the primer, stretching the case walls just forward of the head, and stopping when it hits the bolt face. The thin, forward part of the case expands to fill and grip the chamber while the bullet moves out of the case and down the barrel.Ĥ. If it's not heavily crimped in place, it backs out, shoving the bolt and barrel as far apart as it can.ģ. ![]() The firing pin shoves the case forward, rim against the breech.Ģ. 303 cartridge is fired, a whole string of events occurs.ġ. Since the cartridge is controlled by its rim, this clearance doesn't do any harm (except to handloaders who insist on full-length sizing). In addition, Lee-Enfields and their ammo were often made with a fair amount of space for dirt, mud, snow and other battlefield debris between the chamber and the cartridge's body and shoulder ("Body/shoulder clearance"). Since there has to be some room to allow for varying rim thickness, the headspace is normally a bit more than necessary - giving what I call "head clearance", a little extra space so the bolt can close easily, even on the thickest rim allowed. It's the space where the "head" (rim) of the cartridge fits when the rifle is loaded. 303, headspace is simply the distance between the front of the bolt and the back of the barrel. ![]() Stripped to its essentials, with a rimmed cartridge like the. The truth is less interesting but still worth knowing. Several generations of American shooters have been convinced by bad information that something mysterious and scary called "headspace" should be checked and re-checked on almost any surplus rifle, especially Lee-Enfields. ![]()
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