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Explaining Headspace

75K views 90 replies 50 participants last post by  gdmoody 
#1 ·
I have seen this term in a number of manuals, Headspace of a .45 ACP cartridge, which headspaces off the case mouth but have never understood what it meant.

Can someone explain it to me, in understandable terms, what it means and specifically its relevance to reloading .45ACP.

Thanks in advance.
 
#54 ·
New here. Just been looking around. Been casting bullets and reloading for over 50 years. Rifles, pistols and shotguns. I am impressed. You guys rock. The explanation of headspacing was better than very good by all. For the newbees here you can't go wrong, listen up. These guys know what they are talking about.
 
#55 ·
New here. Just been looking around. Been casting bullets and reloading for over 50 years. Rifles, pistols and shotguns. I am impressed. You guys rock. The explanation of headspacing was better than very good by all. For the newbees here you can't go wrong, listen up. These guys know what they are talking about.
Welcome to TFF lcn ! I grew up in Darrington and have family all around you. I sure don't miss the cold though, alot more nice shooting days down here in TX.

I do miss the size of the muleys though.;)

Glad you enjoyed the headspace thread and appreciate your comments.

Semper Fi,

Woolley
 
#56 ·
Welcome to TFF, Icn. There is a host of experience and shooting wisdom on these forum pages, and people here are glad to share their wisdom and experience with newcomers. Glad to have you aboard and hope to hear from you.
 
#57 ·
Alpo,
I have a .357 Mag Revolver and have been reloading 180-grain cartridges for several years. Recently I purchased a Henry .357 magnum lever action rifle. Will the headspace matter if I shoot the revolver rounds out of my rifle? The salesman at Gander Mnt said that I could shoot the same ammo out of both, but this thread on headspace is making me stop and wonder if there is a different cartridge headspace for a revolver and a rifle.
 
#58 · (Edited)
Headspace is the distance from the bolt face to the reference point on the cartridge. Rimmed cartridges like 357MAG headspace on the front edge of the rim All 357 MAG chambers should be using the same measurement for that cartridge. 357 MAG revolver ammo should fit 357 rifles with NO problem and vice versa if the ammo is made to the specs in reloading manuals or the ammo industry standards for ammo

Any rifle or pistol marked for the same cartridge should be able to interchange ammo if the ammo is made to the standards for ammo and chambers set up by the organization SAMMI, the industry wide organization that all manufacturers follow.

LDBennett
 
#59 ·
The only problem I can see with shooting 180 grain 357s through a lever gun is the length. Standard 357 bullet is a 158. 180 is actually a 35 Remington rifle bullet.

Using that large of a bullet, the overall length of your cartridge might - MIGHT - cause feeding difficulties coming from the magazine to the chamber.

Some - SOME - 357 rifles do not like 38 special ammo because it is too short, and the gun does not like to feed it. There are lots of discussions on cowboy boards about seating bullet long in 38 brass, so they will feed in their 357 rifles.

Logic says that if being TOO SHORT can cause feeding problems, so can being TOO LONG.

Might not have a problem. Your gun might eat 'em up like jellybeans. But it might not. Only way to know is try.

But no, as LD said, there is no headspace problem.
 
#60 ·
I just read though this tread. I also already read the honady manual which I thought did a very good job of explaining it. I thought I understood it until I took a closer inspection of my new glock. I have never owned one before but I shot at least 20 of them and to my memory they all have the part I'm going to refer to. I pretty sure glock is going to call it there loaded chamber indicator. I was never sure why they but it on there because it is not very effective (not that I ever cared). After closer inspection it hooks into the rim of the case. Is these tiny part trying to control head space or is it spaced of the mouth like any other strait walled rimless case?
 
#61 ·
Glocks I believe are as most centerfire delayed recoil operated guns in that the barrel moves a short distance with the slide in recoil, then the barrel stops while the slide continues rearward. The extractor hooks onto the rim of the case to pull the case from the barrel when the barrel stops in recoil and the slide continues reward. The ejector hits the opposite side of the case rim and kicks it off the extractor hook and the case flies out of the gun. Is the extractor what you are talking about?

Here is a schematic link and the extractor is #11.

http://www.brownells.com/schematics/Glock-/Models-17-39-sid858.aspx

When the slide closes on the loaded round, the extractor has snapped over the rim and protrudes from the slide which by chance indicates the chamber is loaded. Other guns use this way for loaded chamber detection. Some have a red dot painted on the top edge so the protrusion of the extractor is easily seen.

The headspace should be on the front of the case on the mouth of the case as in any other center fire gun of this type.

So…. The EXTRACTOR extracts the cartridge from the barrel and the EJECTOR ejects the case from the gun.

LDBennett
 
#62 ·
I just read though this tread. I also already read the honady manual which I thought did a very good job of explaining it. I thought I understood it until I took a closer inspection of my new glock. I have never owned one before but I shot at least 20 of them and to my memory they all have the part I'm going to refer to. I pretty sure glock is going to call it there loaded chamber indicator. I was never sure why they but it on there because it is not very effective (not that I ever cared). After closer inspection it hooks into the rim of the case. Is these tiny part trying to control head space or is it spaced of the mouth like any other strait walled rimless case?
It headspaces on the mouth. I think you're seeing the extractor, which pulls the fired case back out of the chamber after you fire.
 
#68 ·
Alpo, great job explaining it and especially the descriptions for different types of cartridges. I knew the basics but not the information on some of those casings.

A question for you though. How can you adjust the headspace if it's off when you put together an AR from parts?
 
#69 ·
Good question.

With a REAL gun :p a bolt or single shot, if you have inadequate headspace you have the chamber cut deeper. If you have excessive headspace you can have the barrel removed, the face machined down, then have it reinstalled one thread deeper, which gives you inadequate headspace, and you have the chamber recut.

If you are only going to shoot THAT gun in that cartridge, you can build a false shoulder on the case, fireform 'em to THAT gun and neck-size 'em.

But Mr. Stoner's Plastic Fantastic - I don't have a clue.

Sorry.
 
#70 ·
With an AR with a headspace problem you have a couple of ways. First is to try a different bolt. The second would be to pull the barrel and then remove the barrel extension and mill the barrel and ream the chamber back to specs. You've got a new barrel and bolt so chances are slim that you'll have a headspace problem.
 
#71 ·
Is the concept of MIL SPEC AR's to be able to randomly interchanging barrels (with barrel extensions installed) and bolts? Are the tolerances of manufacture and the specification of manufacture such that bolts can be interchanged as can be barrels and still maintain proper headspace tolerances?

Commercial rifles (bolt guns, semi-auto's, levers, pumps) appear to have to have hand fitting of the barrels for headspace. Is it possible that MIL SPEC AR's don't normally need headspace correction?

LDBennett
 
#72 ·
That's the way I understand it LD. The Mil-spec barrels are head spaced during installation of the barrel extension with a mil-spec bolt. Theoretically, it doesn't matter what mil-spec bolt or barrel you use, head space will be correct.

All the stuff I keep seeing is "make sure you check the head space". The reality is though that if it's off a little, there's not really anything you can do about it because there isn't any reasonable way to adjust it anyway.
 
#74 · (Edited)
While it is true that the "step" in a pistol's chamber establishes the upper limit of case length, in reality the straight-walled rimless pistol cartridges only headspace on the case mouth in one special (and rare) circumstance: when the chamber is minimum length and the case is at maximum length. In most everyday instances, the headspace of these cartridges is established by the action of the extractor holding the case head snugly against the bolt face.

This is why it is so easy to fire a 9mm round in a .40S&W, or a .40S&W round in a .45ACP. If these cartridges were truly headspacing on the case mouth they would be rattling around loosely in those respective chambers and never allow the firing pin to make a firm hit.

This is also why it is so uncommon for reloaders to feel the need to trim straight-walled pistol brass. If these cartridges were truly headspacing on the case mouth, case length would be critical. In reality, they're not, and it isn't. Excessive case length only becomes an issue when the case grows so much that the case mouth is bumping up against that "step", in which case the weapon may not have enough headspace to go into battery. Pistol cases usually fail before they grow that much.
 
#75 ·
Welcome to the forum, CaptainGyro. You've found a great place to be. There are probably centuries of experience and libraries of information in the combined membership here, and everyone is glad to help each other out. We're a friendly bunch and enjoy a good chat, a good laugh, and a good discussion. Pull up a keyboard and chair and enjoy!!

What do you shoot?

Be forwarned...this place can become addicting. :)
 
#76 ·
Thank you very much for the welcome. I found the forum while looking for 76Highboy's LNL videos, and it struck me as an intelligent group of folks. I'll try not to drag down the average.

I like to shoot everything, but the hooligans I've fallen in with at the local club are all handgun enthusiasts, so that's where I've been spending most of my time lately. I really enjoy long-range precision rifle, but my local club is limited to 300 yards, so I haven't had the opportunity to really expand those horizons. I recently stumbled onto a Benelli M4 for a good price, so I've been dabbling in a little tactical shotgun too.

I do quite a bit of reloading, and am always anxious to learn something new or share what I've learned.

Again, thanks for the hospitality.
 
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#77 ·
I just found this picture, in Hatcher's Machine Guns.

Shows "Proper Headspace", and the result of "Excess Headspace". Notice the second drawing, the SLIGHT little bit of room between the cartridge head and the bolt face? That's all it takes.
Text Parallel Font Diagram Line art
 
#78 ·
Thanks, Alpo;
That may help to solve a mystery. We were shooting black powder cartridge (Sharps 45-90), and for no apparent reason the cartridges started separating. One day it was shooting fine; the next it was broken cases. I'll pass this on.
 
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