Head space in fire arms

 

Head space in fire arms

Hi guys!

Thanks for tuning into learn about firearm.com

I hope all of you are fine, today we are going to discuss about what is head space in fire arms and what is the vital role of head space in fire arms.

What is head space?

Head space is the total distance between the datum line and the bolt face when the cartridge is chambered. Mostly the head space is measured by using gauges like GO and GO gauge. The below figure clearly represents the head space.

Head space measuring gauge for 7.62 NATO

 

What is datum line?

Datum line is the reference line that is taken for measuring the head space of the fire arm or the dotted line in between the shoulder and the neck of the cartridge.

Mostly, in fire arms the head space is located at a particular spot with in the chamber where the cartridge case stops forward movement during chambering.

The main role or need of the head space is ensure the cartridge is properly fit inside the chamber without interruption.

 

Proper head space is more important for the following reasons:

a)    Safety:

Proper head space ensure that the cartridge is securely and correctly positioned with in the chamber.  If the head space is too tight or too loose, it can cause the firearm to malfunction dangerously, potentially leading to cartridge case ruptures, misfires or even catastrophic failure, posing a serious injury or risk to the operator.

 

b)    Reliability:

Correct head space is essential for the reliable operation of the firearm.  If the head space is not with in specified tolerances, it can lead to issues such as failure to fire, failure to eject, or difficulty to chambering rounds, all of which can compromise the weapons functionality.

 

c)    Accuracy:

Consistent and correct head space contributes to the overall accuracy of the firearm. Proper head space ensures that each round is chambered consistently, leads to more ballistic performances.

 

d)   Longevity of the firearm:

Correct head space reduces excessive wear on the firearms components.  Incorrect headspace can cause undue stress on the barrel, bolt and other parts, shortening the service life of the firearm and potentially causing damage that can be expensive or difficult to repair.

 

Let us go and see what kind of problems can cause due to excessive head space and insufficient head space.

 

                         I.          Excessive head space:

 

                                              i.          Case rupture: when head space is too large, the cartridge case may not be adequately supported.  This can cause the case to stretch excessively or even rupture upon firing, releasing high pressure gases that can damage the firearm and it cause injuries to the operator.

 

                                            ii.          Misfires and light strikes: with excessive headspace, the firing pin may not strike the primer with sufficient force, leading to misfires or light primer strikes.

 

                                          iii.          Inconsistent ignition: The cartridge may not be positioned consistently, leading to erratic ignition and poor ballistic performance, which impacts accuracy.

 

                                           iv.          Increased wear: The bolt and barrel extension can experience undue stress, accelerating wear and potentially causing premature failure of these components.

 

                      II.          Insufficient head space:

 

                                              i.          Difficult to chambering: If the head space is too tight, it can be difficult or impossible to chamber a round properly, leading to feeding issues.

 

                                            ii.          Failure to fire: A tightly chambered round might not allow the bolt to locked properly, preventing the firearm from firing.

 

                                          iii.          Increased in pressure: Tight head space can cause excessive pressure build up in the chamber when a round is fired, which can result in damage the components or case head separation.

 

                                           iv.          Extraction problems: May be the case stuck inside the chamber after firing, it can lead to extraction and ejection problems.

 

                   III.          General operational malfunctions caused due to excessive and insufficient head space:

 

                                                i.          Jamming: Excessive and insufficient head space leads the malfunctions like jamming, failure to feed, failure to fire, and failure to eject.

 

                                              ii.          Damaging the bolt and receiver: Continuous firing with improper head space can cause deformation in bolt, bolt carrier and receiver and making the fire arm unworkable.

 

                    IV.          Safety hazards due to excessive and insufficient headspace:

 

                                              i.          Blow back tendency: Improper head space can prevent the bolt from fully locking and it can cause the fragments of the case or the high-pressure gas can escape through the breech of the barrel towards the shooter and cause a serious injury.

 

                                            ii.          Catastrophic failures: continue the firing with improper headspace can leads to explodes the firearm and cause sever injury and make firearm unworkable.