I seriously doubt this is case head separation but what do you guys think?

[J E Custom]

1. Head clearance is the air space between the rear of the case and the bolt face. And the head clearance is equal to the amount of shoulder bump. The rifles headspace is the distance from the bolt face to the datum point on the chambers shoulder.

Wrong again. Head space is the air space between the Head space gauge and the bolt face. WE don't set head space with a cartridge If we want it to be precise. Head space will change from one brand of cartridges to the next, because they have a minimum and maximum specification that gives them a range of lengths that they have to manufacture their ammo buy and it is normally in the middle of this range so it will chamber in most all chambers. Some manufactures like Winchester will tend to size their ammo On the small(Short) side and others will size their cartridges near the maximum length like Hornady and if a chamber is cut to minimum length, Some ammo will not chamber. Head space is therefore normally set 1 to 3 thousandths more than the head space gauge. Once they are fired, essentially there is no head space until it is sized. and depending on the sizing philosophy, there may still be no head space. PS: I cant find any head clearance gauges, Only Head space gauges.

2. The OP didn't need to take the rifle to a gunsmith and check the headspace. The OP cases grew in length when full length resized and squeezed making them longer in over all length.

In the beginning he did not know what the problem was and was looking for a way to find out if he had excessive head space that could cause case head separation. Without the proper head space gauges That any gunsmith would have it would be just a guess so he solved the question by sectioning and eliminated the question.



1. The primer is the first thing to move to the rear when the cartridge is fired by the amount of head clearance.

2. P.O. Ackley did a experiment with a 30-30 Winchester rifle and removed the rifles locking bolt. He then remotely fired the rifle and the only thing that happened was the primer moved to the rear. When the cartridge fired the body of the case gripped the chamber walls and the chamber pressure was not great enough to cause the case to stretch to meet the bolt face.

This one still makes me laugh because first, How would you know if the primer moved or not, unless you had a bad load or a concaved bolt face that would allow the primer to protrude enough to feel it or had a primer pocket that was expanded bad enough not to hold the primer in the first and/or it was over pressured enough to let it blow and we all know what this leads to. I have fired thousands of military ammo that the primers were sealed and even sealed lots of primers my self and the seal never broke even though the primer was flattened because it didn't move. So if you are having this problem you have something wrong with your firearm or your loads.

I am a big fan of PO Ackley and read almost everything he wrote and
he did lots of testing on things that would not be normal and he himself said many times that you should not try this test because it could be fatal if not under controlled conditions. He also blew up many different actions to see how strong they were. Also he decided that if you reached enough pressure that the primer would be blown out and so would the cartridge once it reached enough pressure to overcome the case grip on the chamber. and without the bolt to restrain the case and the primer all of it would be blown out. (The reason for the bolt in the first case) and it would result in one shot only by the shooter). Excessive head space is the main reason case head separation occurs with cartridges whether it is built in to the chamber buy poor head spacing or over sizing cases when reloading them. The only other cause is case fatigue
from many firings and over pressuring the case.


J E CUSTOM

 

[Edd]

From the SAAMI Glossary.......

HEAD CLEARANCE
The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.

HEADSPACE
The distance from the face of the closed breech of a firearm to the surface in the chamber on which the cartridge case seats.

HEADSPACE GAGE
A device used in a firearm to determine the distance between the breech face and the chamber surface on which the cartridge seats. Also called Breeching Plug.

 

[26Reload]

So the difference between Headgauge and Headspace is the Headclearance?

 

[Edd]

So the difference between Headgauge and Headspace is the Headclearance?

Sort of but not exactly.

Head clearance is measured with a cartridge.

A gunsmith can chamber the barrel so there is clearance between the bolt face and the headspace gauge or he can chamber it where there isn't any clearance. A reloader can size the cases so the clearance is whatever he wants it to be regardless of the headspace.

After the chamber is cut, the headspace never changes but the clearance can.

An example,... a Gunsmith cuts the chamber so there is zero clearance between the Headspace Gauge and the bolt face. A reloader can resize his brass to get .002" Head Clearance.

Another Example,... a Gunsmith cuts the chamber so there is .004" clearance between the Headspace Gauge and the bolt face. A reloader can resize his brass to get .002" Head Clearance.

One of those chambers has .004" more Headspace than the other but they both have the same Head Clearance.

 

[Barrelnut]

From the SAAMI Glossary.......

HEAD CLEARANCE
The distance between the head of a fully seated cartridge or shell and the face of the breech bolt when the action is in the closed position. Commonly confused with headspace.

IMO, instead of "Commonly confused with headspace". it should say "headspace" is commonly used interchangeably with "head clearance" with the definition defined by the context of the conversation.

 

[bigedp51]

Head clearance is how much shorter the case is than the chambers actual headspace.
Meaning if you bump the case shoulder back .002 when full length resizing you will have .002 head clearance.

And when the cartridge is fired the case will grip the chamber walls, and the primer backs out of the primer pocket. Then as the chamber pressures increases the base of the case stretches to contact the bolt face.

This is very simple to see when you make a workup load and starting at the suggested start load. At the start loads the primer will be protruding from the base of the case. Then somewhere around the middle of the workup load the primers will be flush with the base of the case. Then as the chamber pressure increases even more the primer will start to flatten around the edges.

Bottom line, anyone who has ever made a workup load with new cases would have seen this. And I have new cases that were .011 shorter than chamber headspace. Meaning even with bad eyesight if you rubbed your finger over the base of the case you can feel the primer protruding.

And yet we have a "expert" in this forum who tells us the primer never moves.

 

[bigedp51]

The SAAMI chamber and cartridge drawings has headspace listed as min and max with .010 between the two settings.

In the SAAMI drawing below for the .308 Win it lists 1.630 min and 1.640 as max
There are three different headspace gauge lengths GO, NO-GO and Field and Field is the maximum safe headspace length.

Below are three British headspace gauges, the GO is .064, the NO-GO is .067 (American SAAMI standards)
and max is .074. (or SAAMI Field)

The British military only used the .064 and .074 gauge and long as the bolt did not close on the .074 gauge the rifle was in survivable condition.

Below is my Colt AR15 Field gauge at 1.4736 and as long as my AR15 bolts do not close on this gauge my AR15 is within safe headspace limits. Meaning a new rifles headspace is set between the GO and NO-GO gauges and as the rifle wears the headspace is allowed to increase beyond the NO-GO gauge and to the Field gauge limits. And my AR15 carbine has to wear .0066 before reaching Field gauge limits.

 

[bigedp51]

And this posting is for J E CUSTOM to "READ" and right out of the Sierra reloading manual.

Read the bottom paragraph and learn something and stop telling people the primer never moves.

The primer on the left below has backed out on a old worn Enfield rifle that is beyond the .074 headspace limits. This cartridge was fired with reduced loads for cast bullets at low chamber pressure.

And before this posting I checked some of my 30-30 reloads and could feel the protruding primers with my finger. And when a straight edge was placed on the primer you could see daylight around the base of the case. And these cases were loaded with a 150 grain bullet and 38 grains of 748 and the Hornady manual lists 38.9 grains as a maximum load.

 

[J E Custom]

Sort of but not exactly.

Head clearance is measured with a cartridge.

A gunsmith can chamber the barrel so there is clearance between the bolt face and the headspace gauge or he can chamber it where there isn't any clearance. A reloader can size the cases so the clearance is whatever he wants it to be regardless of the headspace.

After the chamber is cut, the headspace never changes but the clearance can.

An example,... a Gunsmith cuts the chamber so there is zero clearance between the Headspace Gauge and the bolt face. A reloader can resize his brass to get .002" Head Clearance.

Another Example,... a Gunsmith cuts the chamber so there is .004" clearance between the Headspace Gauge and the bolt face. A reloader can resize his brass to get .002" Head Clearance.

One of those chambers has .004" more Headspace than the other but they both have the same Head Clearance.

This is correct !!! Once head space is set, it will not change. the Reloader can change the case clearance with the dies but not the head space.

Thank you ED

J E CUSTOM

 

[26Reload]

Okay...HEADSPACE...measurement from bolt face to shoulder contact..
Headclearance can be .002" and bumped back shoulder can be .002"...
..so changing a cartridge from a standard to an AI...
Is changing "Headspace"...if the shoulder is cut to different tolerances....

 

[J E Custom]

And this posting is for J E CUSTOM to "READ" and right out of the Sierra reloading manual.

Read the bottom paragraph and learn something and stop telling people the primer never moves.

The primer on the left below has backed out on a old worn Enfield rifle that is beyond the .074 headspace limits. This cartridge was fired with reduced loads for cast bullets at low chamber pressure.

And before this posting I checked some of my 30-30 reloads and could feel the protruding primers with my finger. And when a straight edge was placed on the primer you could see daylight around the base of the case. And these cases were loaded with a 150 grain bullet and 38 grains of 748 and the Hornady manual lists 38.9 grains as a maximum load.

You just stated my case for me. If the primer pocket is a lose fit or the bolt face is dirty and the primer can back out and stay there and/or if the pocket wont hold the primer in place at ignition, The case is no good and should be discarded. Primers are supposed to seal to prevent any leakage that can turn into gas jetting that will damage the bolt face.
I said earlier in a post that if something was wrong with the firearm this could/would happen if the primer could stay out of the case when fired.
This would be another good reason to only size the minimum so the case head would stay in contact with the bolt face and prevent any possibility of it happening, even though I have never seen it and don't believe it. The primer you show doesn't look fired and you have something wrong. the fact that the rim of the case you show is thinner will still not allow the primer to stay out unless the bolt face is concave and allows it to. If your bolt face is bad enough to leave the primer sticking out that much, It should be refaced OR RETIRED. If your reduced/squib load does not have enough pressure to push the case against the bolt face you may have a bigger problem.

Weather we agree or disagree, this is not a usual condition and could be dangerous. another thing, I have tested firing pin strikes by priming only (No Powder) and even though the case still had case clearance it still never backed out.

I have never seen this problem because it does not exist in firearms in good working order or loads loaded correctly. and I'm not fast enough to see the primer pop out and then go back in during the burning of the powder charge. so giving that you may have, I would recommend that you have a gunsmith look at it and an experienced Reloader give you a hand.

J E CUSTOM

 

[J E Custom]

Okay...HEADSPACE...measurement from bolt face to shoulder contact..
Headclearance can be .002" and bumped back shoulder can be .002"...
..so changing a cartridge from a standard to an AI...
Is changing "Headspace"...if the shoulder is cut to different tolerances....

The AI designed cartridges normally have the same shoulder to neck junction length minus .004 to .006 thousandths so the parent cartridge can be fired in it safely. The datum line does however change and the body length is increased with the Improved/changed shoulder angle giving the case slightly more case capacity. If you buy an AI head space gauge it will have the 40o (Or what ever shoulder angle you want on it) bur the standard parent case head space gauge can be used by someone that knows the difference.

With the exception of the new 280 AI the other AIs will/can use the parent head space gauge unless it is wildcatted and other dimensions have been changed.

J E CUSTOM

 

[Edd]

Okay...HEADSPACE...measurement from bolt face to shoulder contact..
Headclearance can be .002" and bumped back shoulder can be .002"...
..so changing a cartridge from a standard to an AI...
Is changing "Headspace"...if the shoulder is cut to different tolerances....

Using the .308 drawing from post #161, if you change the shoulder angle from 20° to 40°, the distance from the bolt face to the .400" diameter point on the shoulder will increase .0418".

 

[bigedp51]

This is correct !!! Once head space is set, it will not change.

J E CUSTOM

Wrong again, the headspace increases over the lifetime of of the rifle. Excessive bolt thrust can cause bolt lug setback and a increase in headspace. Oil, grease and water in the chamber can cause excessive bolt thrust and double the normal amount force applied to the bolt face. If the bolt lugs are not lubed this can cause wear and over time the headspace will increase. Hot loads will increase the headspace faster than light or normal pressure loads.

Bottom line, if the rifles headspace never changed after it is initially setting you would not need a Field gauge. Checking headspace, is like checking how much tread is left on your tires. And headspace will increase just like your tire tread depth will decrease with wear.

Why should I care about my rifle's headspace?
http://thecmp.org/training-tech/armorers-corner/headspace/

The three gauges you will encounter are the "GO", "NO GO" and "FIELD". CMP only uses "GO" and "NO GO" gauges but I will describe all three.

The "GO" gauge - is most commonly used when installing a new barrel and reaming the chamber to size. The bolt should fully close on the "GO" gauge, if it fully closes you can be sure you have enough room in the chamber to prevent the cartridge from being crushed during chambering. The "GO" gauge can also be thought of as a minimum safe headspace gauge and the rifle's bolt must be able to fully close with it in the chamber.

The "NO GO" gauge - is used to make sure a firearm does not have excessive headspace. The bolt should NOT fully close on the "NO GO" gauge, if the bolt cannot be closed on the "NO GO" gauge then you know your rifle does not have headspace that is excessive. The "NO GO" gauge can be thought of as a maximum headspace gauge and should not be able to fit in the rifle's chamber with the bolt fully closed. If the bolt DOES close on the "NO GO" gauge, it does not necessarily mean that the rifle is unsafe; it does however show that a further check with the "FIELD" gauge would be necessary to determine if it is safe to shoot.

The "FIELD" gauge - is used to check absolute maximum headspace. If the bolt closes fully on the "FIELD" gauge the rifle IS NOT to be fired and should be considered unsafe to shoot. CMP does not use this gauge because rifles that pass the "FIELD" check but fail the "NO GO" are approaching the point where they will be unsafe to shoot. Our standard for maximum headspace is the "NO GO" gauge to ensure our customers will be able to shoot safely for many years.