Headspace

[steve-o 1911]

I'm not sure where to ask this question about the term Headspace. What does it mean? I read up on it alittle and kinda know what they are talking about, but why is it so important? do you need to know this if your reloading, and do i have to worry about it on my 1911 45 and AR-15 223. I'm new to this, so help please

[CowTowner]

I would think this one would be better asked in the "Smithy" area.
I think I know what headspace is, but since I'm no expert, I'll choose to not show my ignorance in public. (any more than I already have done in the past)

[cdrt]

What is Headspace?
by Walt Kuleck

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For those of us who are relatively ignorant and/or inexperienced as gunsmiths, could you be "technical" for a bit about the subject? What exactly is headspace? Where is it? What are the tolerances, etc?

There are two ways to look at headspace. First, let's consider the practical definition, and follow up with the technical one.

In practical terms, headspace is the clearance allowed between the base of the cartridge case and the face of the bolt. The position of the cartridge in the chamber is controlled in a variety of ways depending on the type of cartridge case involved. Most rimless automatic pistol cartridges (e.g., 9x19mm Parabellum, .45 ACP) are positioned by the case mouth resting on the front edge of the chamber. Rimmed cartridges (e.g., .45 Colt, .30/30 Winchester) are positioned in the chamber by the face of the rim resting on the rim recess at the back of the chamber. Belted magnum cases (e.g., .300 Win Mag., .458 Win Mag.) are positioned by the belt resting on the recess provided for it at the rear of the chamber, much as rimmed cartridges are. Finally, bottle necked rimless cartridges are positioned by the shoulder of the case resting against the shoulder of the chamber.

So when a cartridge is chambered, it is positioned in one of the above ways. Once positioned, there must be a little free space between the cartridge case base and the face of the bolt, to allow for dimensional tolerances in cases. When the cartridge is fired, the case expands in all directions, including toward the bolt face. If there is the intended clearance space, the case head is not stretched excessively during this expansion. If the space is too much, as the case head is pushed backwards towards the bolt face it may stretch enough for it to significantly weaken the case in the area just in front of the thick portion of the case head, called the web, where the thinner walls of the powder containing part of the case begin. If the case head does not separate on the first firing, the weakened brass may do so on subsequent firing. This is a very bad thing, as hot gas at 50,000 psi will damage at least the stock and magazine, if not the firer's hands or face. Little drops of molten brass and brass shards are carried by the hot gas at near-supersonic speeds. If all the firer gets is a Chicken Pox-like tattoo, he or she is fortunate.

[Bullet94]

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.


http://www.saami.org/Glossary/index.cfm


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[saudst]

cdrt, did you copy that out of a manual? That is one of the most right on explanations I've heard or read on headspaceing. +1

[saudst]

Sorry, I just caught the begining of your explanation. +1 anyway

[cdrt]

It's from the Fulton Armory website.

[WSM MAGNUM]

Excessive headspace is also the main cause of misfires as well. As a reloader you should know what the headspace is on each of your guns.

[Gbro]

My 1st introduction to Head spacing was when the DI told me to give him "10".
Then came the "Go - No-Go gauge on the M-2.

[Alleykat]

You'll never have to worry about headspace in loading .45ACP. For .223 reloading, I strongly recommend the Wilson case gage for setting up the sizing die, so that it properly bumps the shoulder for the correct headspace.

[saudst]

This makes me think of a question I've thought of for years. If a belted bottle neck case headspaces on the belt, alot of "experts" say this is inferior to headspaceing on the shoulder, then why could'nt you just partialy size a belted case and make it headspace on the shoulder. I realize this would only work on the chamber that the case was fired in to begin with, but if I only own 1 .300 mag. is there any reason why this would'nt work? I know we have neck sized only for the same reason for years, to match the chamber as closely as posible. I figured since we were on the subject, sorry if I'm out of line.

[ForneyRider]

I like the Dillon case gages. They are stainless steel. The L.E. Wilson gages are aluminum.

When seating bullets, you have to compromise when the magazine is too small.

My 7mm Mag rounds are set to max to where they will still load/feed the magazine. This is much shorter than if I were to use the rifle like a single shot and just load one round directly into the chamber. Both of these lengths are longer than if I use the cannelure to decide the bullet depth.

My 45ACP, being shot in semi-auto, is set to same length as some factory ammo I had on hand: 1.24in for 230gr FMJ and 1.2in for 230gr JHP.

[WSM MAGNUM]

You'll never have to worry about headspace in loading .45ACP.

Not entirely true. You can have headspace problems if you let the cases get too long or too short. And if you crimp them too much you will also have headspace problems.

[steve-o 1911]

Thanks guys for all the info. Im gonna be starting to reload .223 soon, so if I bought a headspace gauge is it pretty simple to use and figure out. Or do you guys have suggestions. Thanks

[Don H]

You can have headspace problems if you let the cases get too long or too short.

Back about 35-40 years ago, I ground about 1/10"" off some .45ACP and 9mm cases, loaded them like normal-length rounds and fired them, mixed in magazines with normal-length rounds. The .45 was shot in a Colt Commander and the 9mm in a Browning High Power with internal extractor. Couldn't tell the difference between the shortened cases and the regular cases, either in the report/recoil or the function of the pistols.

Let's use the .45ACP in a 1911-pattern pistol for an example. As the slide goes forward and picks up a cartridge from the magazine, the rim slides up between the breech-face and the extractor. A properly adjusted extractor holds the case tightly against the breech-face. In effect, the cartridge headspaces on the extractor because it's the extractor that prevents it from moving forward.

[WSM MAGNUM]

In my experience you should not be using the extractor solely for the case to headspace on. It was designed to headspace on the mouth of the case in the barrel.
I think most problems people have with their ammo in their guns is because most do not fully understand what headspace is, and how it is supposed to be measured and then corrected in that type of gun.

[T. O'Heir]

"...headspace is the clearance allowed between the base of the cartridge case and the face of the bolt..." Um, no. It's the manufacturing tolerance between the bolt face and a spot in the chamber that allows cartridges made by all manufacturers to be used in firearms chambered with the same cartridge. How said cartridge is positioned in the chamber has nothing to do with it.
Where a particular cartridge type headspaces varies though. Rimless pistol cases headspace on the case mouth, rimless rifle cases on a spot on the shoulder, rimmed on the rim and belted magnums on the belt.
If the headspace is excessive, the force applied backwards by the recoil can cause a catastrophic failure due to the case coming back with excessive force. Too little and the case won't fit properly in the chamber.
A case length guage has nothing to do with headspace. Cartridges, loaded or not, do not have headspace. Case length guages are just a quick way of checking cartridge OAL.
The extractor has nothing to do with headspace. It's sole purpose is to pull the spent case out of the chamber after firing. No cartridge headspaces on the extractor groove.

[Bullet94]

If your going to check headspace I recommend the RCBS Precision Mic.


Quote:
A few twists of the Precision Mic and you'll know your chamber headspace and bullet seating depth to 0.001". The Precision Mic measures from a datum point on the case shoulder to the base, giving you the exact SAAMI tolerance readings. An indispensable tool for safe, accurate loads that extend the life of your brass and firearm.


http://www.midwayusa.com/esearch.exe...in+Search.y=11


From SAAMI -

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

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[jamaica]

I think headspace is determined by the manufacturers. It is built into the gun.
I have never had any reason to worry about it.

Another question:

When the cartridge is fired, the case expands in all directions, including toward the bolt face.

If this is so, then how come when you fire a rimmed cartridge in a revolver the rim is always forward against the cylinder? It is a good thing that it is or one shot is all you would get.

[jhansman]

Man, I have read more definitions of headspace than I can count, and none of them have yet led me to an understanding. I am visual learner, so any kind of graphic on this concept would help me (and countless other, I suspect) finally grok this term. Can anyone create a graphic representation for we who need it?

[Bullet94]

Here is a link with a picture -

http://en.wikipedia.org/wiki/Headspace


And others that might be of interest -

http://www.rifleshootermag.com/gunsm...eadspace_0612/

http://www.ar15.com/content/page.html?id=71


When you resize your case you aren’t reducing headspace but rather reducing the distance between the base of the case and the datum point on the case shoulder. A RCBS Mic measures this distance on a fired case and can be used to tell how much you’ve reduced this measurement by resizing. There by allowing you to not size your case more than desired. A Mic is used to accurately set the amount your sizing your cases. As an example when I resize my cases for my AR, I measure a fired case and then adjust my sizing die to resize the case .002 to .003 smaller between the base of the case and the datum point on the case shoulder (and by the way this measurement is different for each of my AR’s). This amount of resizing is enough for reliable chambering with out sizing my brass more than necessary.


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[jamaica]

This is crude, but maybe it will help.

In rimless, the shoulder hits and there is a space between the bolt and the casing.

In rimmed, the rim hits the barrel and there is a small space .

In belted magnums the belt hits in the recess and leaves a space between the bolt and casing.

In 45 ACP the front of the casing hits setting the head space. ( some say)

Any way the specs call for certain standard dimensions and if the guns are within spec and the ammo too then the head space is correct.

Incorrect head space can cause stretching in the web and possible ruptures in this area.

[jamaica]

A little space is needed to accomodate some variations in both the guns and the ammo. Reloading dies should put the casing back within spec. Check the length of the brass. If your gun is built right and in proper condition you should not have much to worry about. It is good to know what is going on though and what might happen if things are not within spec.

[Bullet94]

Your drawings look good.
The space show in these drawings is sometimes mistakenly referred to as headspace but it is really the head clearance.

[Alleykat]

like the Dillon case gages. They are stainless steel. The L.E. Wilson gages are aluminum.

So, you think maybe the solid steel L.E. Wilson .223 case gage I have is the only non-aluminum L.E. Wilson case gage in existence?? (Or, have you just never inspected a Wilson case gage?)