Dies for Bumping Shoulder

[pwc]

HiBC, So, you call this esoteric "space" by its common name too.

The how and why of this headspace is well known, as is the adjustment to sizing to optimize it.

By the way, my sock drawer is now lint free, and I found an old military pocket knife too.

[HiBC]

My "seat of the pants" answer,freebore,throat,leade….I'll risk being wrong.

Freebore is a term that we started using regarding Weatherby reaming a long throat to ease pressures. Its nuanced toward relieving pressure.

Throat...from the neck portion of the chamber,the throat is a section of bore reamed free of rifling,generally bore dia.Intent is likely to facilitate loading a bullet without engraving the rifling .Its easier that way. Length may be optimized to suit the bullet,LOA,and desired "jump" It pilots the bullet from cartridge case to bore. Purpose,centering and aligning bullet to bore

Leade,as I understand it,is the transition from no rifling to full rifling,. The angle the lands are cut .It is where the bullet is engraved.. Might be tuned for ogivemjacket hardness,etc

No doubt I'm some percentage wrong. I did not look it up

FWIW,even with a very sharp cutter,there will be some trace of a burr on the trailing edge of an interrupted cut. The trailing edge of the leade will have some degree of burr.
And for all the care a barrelmaker may put into rifling and lapping a bore,its the gunsmith turning a reamer that cuts the throat and leade.

There may be other cutter marks perpendicular to bullet travel. These are put there after the barrel is shipped.

I'll agree we have no need to break in the work of a good barrel maker. We just need to "Do no harm" to the work of the barrelmaker.

Those burrs and imperfectins cut and scrape copper bits from the jacket that may be deposited in the bore. Its my opinion that until these burrs are broken and worn off,its a good idea to remove these bits of copper from the bore rather than shooting over them.

That,IMO,is what a "break in" procedure is about.

Simply "Doing no harm" Its not about finishing the barrel makers work.

[Bart B.]

Look 'em up in

https://saami.org/saami-glossary/

You may realize you were not wrong but just weak in being right according to the industry standard. No big deal if you're emotionally stable.

[Unclenick]

Bart,

I was thinking of the original Mauser designs. In my '96s and '98s, the ejector is fixed to the receiver and the case head doesn't find it until the bolt has extracted the case fully to the rear so it will clear the ejection port.

Originally Posted by Metal God

If you ask me ( which nobody did ) using the word cartridge instead of case is wrong in many ways and is in fact confusing .

And yet, here's a brand fresh example in Glen Zediker's Nov. 1 blog for Midsouth, where he says:

Originally Posted by Glen Zediker

"Beyond {a} good caliper…there’s a very short list of measuring tools I will recommend as “must haves.” Top of that list is a cartridge headspace gage (which is used with that caliper)."

My point is that believing something is universally understood is an assumption. It's based on the idea other people hear the words the way you do. Yet, traveling to different parts of the country, you find usage isn't always universal. If a northern woman says "bless your heart", it means something completely different than it does coming out of the mouth of a southern lady. When I lived in Pittsburgh, I knew the meaning of the question, "'juns go to the store?" Most of the rest of the country doesn't recognize a truncation of the grammatically incorrect "did you ones", but in P-burgh, you do. Usage being regional is not unusual, and I'm starting to wonder if shooting forums qualify as a region, linguistically?

So the basis of my concern is unchanged. I can read "case headspace" or "cartridge headspace" to mean either a property of the case or cartridge, as you do, or as space in the chamber to accommodate a case or a cartridge, as the link I provided previously does. The only way I know to put a final nail in the coffin of that ambiguity is by employing a unique term that doesn't modify an existing term that means something different in a misinterpretable way.


Pwc,

You are correct the discussion has digressed. I don't think you can call it esoteric when most everyone seems to be aware of the terms, even if we aren't agreed on definitions, but it seems a bit nit-picky, I suppose, and wouldn't be worth bothering with except that we have to keep explaining it to newbies.

The original question was just about "bumping" shoulders, a term I believe has caused its own controversy as to whether or not a shoulder can be bumped because it then sounds like the shoulder exactly as-currently-constituted, is being moved back. My own take is the originators meant the case shoulder was bumped-into by the die shoulder, and that resulted in reconfiguring the case so a comparator gives you a thousandth or two lower numbers. I believe the term was originally applied to employing a special die made from a blank by your riflesmith and cut using the same reamer used to cut the chamber. A "bump die" thus configured did not narrow the case appreciably. Its shoulder just bumped into the case shoulder while the sides of the die merely ensured the resulting case still chambered. Thirty years ago, Precision Shooting had ads for the die blanks.

What are sold now as the bump dies, cannot possibly have those customized dimensions. So I thought I would call Forster and ask how their Bushing Bump Dies differ from other sizing dies. It turns out they are a bushing-type neck-sizing-only die, except they are cut it near the shoulder to match SAAMI minimum chamber dimensions. That way you can bump the die's shoulder into your case shoulder without spreading the lower corner of the shoulder beyond what will chamber. In other words, it forces the extra brass from extruding the shoulder back to flow into the neck and not radially outward. If you have a SAAMI maximum diameter chamber, I suppose your case might experience a slight squeeze when it gets to the to end of the die, but normal springback will keep that small and nothing like a normal FL resizing die would squeeze it.

If eliminating pressure ring stretching is your main interest, it is worth looking at Varmint Al's site . He shows that even with full-length resizing, a highly polished chamber does not, as many fear, cause excessive bolt thrust,
and also shows that a polished chamber surface spreads out the portion of the brass over which stretching occurs. In other words, pressuring ring thinning is still there but becomes distributed over a half an inch or more of the case rather than focused over the short distance where the body departs the head, and that prevents the sharp thinning you normally get with a case sticking hard to the chamber wall.
Board member Slamfire has accomplished the same thing in the Garand by oiling cases to make them more slippery. You can FL resize and load them 20 times, and the sectioned case still doesn't show a distinct pressure ring location.

[HiBC]

Look 'em up in

https://saami.org/saami-glossary/

You may realize you were not wrong but just weak in being right according to the industry standard. No big deal if you're emotionally stable.

Thanks,I'll agree my answers could use some "accurizing" Key concepts are "tapered" vs "cylindrical" and the "from" and "to" of the taper.

I also noticed this statement by SAAMI,which seems to allow for the evolution of a term such as "cartridge case headspace length"

The Glossary of Industry terms has been compiled by SAAMI’s Technical Committee to facilitate technical interchanges between members of that committee. It is not intended to provide legal definitions of the terms included, and, in light of further experience, the definitions of these terms may change. It is not intended to be comprehensive since it does not cover the full range of the diversity of the sporting arms and ammunition industry’s products. It is, in other words, a working draft that, it is hoped, may be useful in addressing certain technical matters frequently considered by the Technical Committee and is subject to further change and refinement.

[Metal god]

My point is that believing something is universally understood is an assumption. It's based on the idea other people hear the words the way you do. Yet, traveling to different parts of the country, you find usage isn't always universal

OMG , that's kinda been the point all along and yet we have a select few that insist it's only there way or the high way . Even though through out "our" community (country) many use other these terms that many understand to have two possible meanings . just like words having different meaning in different parts of the country . With all do respect ( and I mean that ) just because you and Guffey say it's so , doesn't make it so .

The term/word is not going anywhere .

[Bart B.]

I had a half hour chat with SAAMI some years ago about this bottleneck case dimension that's in all their case drawing's specs. The rep said it comes up once in a while in their technical committee meetings but never formally addressed nor named. He agreed "case headspace" is a popular and useful term but their technical committee has to agree first before it's formalized then put in their glossary.

[Bart B.]

Originally Posted by HiBC

FWIW,even with a very sharp cutter,there will be some trace of a burr on the trailing edge of an interrupted cut. The trailing edge of the leade will have some degree of burr.

And for all the care a barrelmaker may put into rifling and lapping a bore,its the gunsmith turning a reamer that cuts the throat and leade.

There may be other cutter marks perpendicular to bullet travel. These are put there after the barrel is shipped.

I'll agree we have no need to break in the work of a good barrel maker. We just need to "Do no harm" to the work of the barrelmaker.

Those burrs and imperfectins cut and scrape copper bits from the jacket that may be deposited in the bore. Its my opinion that until these burrs are broken and worn off,its a good idea to remove these bits of copper from the bore rather than shooting over them.

That, IMO, is what a "break in" procedure is about.

Simply "Doing no harm" Its not about finishing the barrel makers work.

The several 7.62 NATO Garand service grade barrels I wore out were broach rifled with a single pass of the tool. Then chambered with the standard milspec reamer. They all tested about 2/3rds MOA at 600 yards with 190 grain hand loads, no break in whatsoever.

Never broke in any bolt gun match barrels either

[44 AMP]

Ihre Probleme seit den Englisch Eine verrueckte Sprache sind.

but then every language is to some degree, and words have multiple meanings due to different contexts.
And, "technical" jargon and use complicates things even further.

It often helps to have an understanding of the history of the terms, which are often carryovers from much earlier times where the object being referred to has changed radically but the old term is still used.

Ball ammunition, for one classic example. At one time all ammo was balls. Then what was being fired became bullets, but was still called ball ammo, and today the term refers to full metal jacket military ammunition.

Cartridge names can be misleading. The 38 Special shoots 35 caliber bullets.

Cartridge names are whatever the maker wants to call them, and can be misleading. In the case of .38s shooting .35 bullets, that's due to technology. Specifically, the change from ouside lubricated heel type bullets (still used in .22RF) to inside lubricated bullets and later jacketed bullets. The heel type bullet is the same diameter as the outside of the case. Those old .38s were actually .38 bullets. Today the case is still the same size (.379" for .38 spl and .357mag) but the bullet diameter has been reduced to .35"

Freebore existed before Roy Weatherby made it a "selling point" of his rifles. It is the distance between the end of the chamber and the beginning of the rifling. Weatherby just did his longer than usual, and made claims about how it improved things.

leade is the leading edge of the rifling, the sloping part so that the bullet doesn't hit a "square shoulder" but eases into the rifling through a tapered area.

Headspace, well think about the earliest days of self contained metallic cartridges, they all had rims. The space in the gun for the case head to fit in was the "headspace". All rounds were headspaced on the rim. Early bottle necked cases also heaspaced on the rim. The term was kept unchanged when rimless cases developed. Its the space in the gun where the cartridge case goes. Those saying a case doesn't have headspace aren't technically wrong, but they aren't explaining anything else beyond that.
A headspace gauge doesn't have headspace (no case fits in it) its used to check the gun's headspace measurements.

A gunsmith creates the guns headspace when installing the barrel /reaming the chamber. Context matters.

I don't see where its so complicated..but then that might just be me, gunsmith training and decades of using terms the same way I still do.

[HiBC]

Another consideration came to me.

Suppose we have two blocks of steel.Nice,ground,square. We alsu have a dowel pin. We want a hole through each block. We want a sip fit on one,and a press fit to the dowel pin on the other.

What is dimensioned on the drawings? What can we measure and control?

While ultimately we might be concerned with the press fit interference and the slip fit clearance,how do you measure .0002 interference?How do you measure .0005 clearance?

We generally don't . We measure the pin diameter, and the hole diameters. We deduce the clearance or interference.

One lesson the Old Machinist must get across to the newly graduated engineer is that the Old Machinist must be able to measure whatever is dimensioned on the print. It seems the academics often overlook things like that in school.

So,yes,after the rifle is built and we are reloading ammo for it,we may ultimately be concerned with head clearance.

With the cartridge case in the chamber ,and the bolt closed and locked,how do you measure head clearance?

I'm talking about using tools a handloader might be likely to own Something that can be ordered from Sinclair or Redding or Forster for under $200

Most of us have never actually measured head clearance.

We deduce head clearance . While there may be different methods,we generally begin with a fireformed cartridge case. Whether by using Unclenick's hardware store bushing,or Hornady's caliper clamp n kit,calipers and a Wilson Bushing gauge,or an RCBS Precision Mic.we generally take a measurement of the cartridge case from case head to the shoulder datum circle as our tools represent it.

We start with that measurement from the cartridge case. That IS the measurement most of us can make,and can use.

Why can't we have a name for that measurement?

From there,we adjust the die for a desired shortening of that measurement,"The Measurement with No Name" to deduce we MAY have a desired head clearance that typically exists only in our minds because we can't go inside the locked chamber to measure it. But that deduced "head clearance" is politically correct to talk about.

A friend recently posted a pic of a very nice buck taken at a lasered 555 yds by a young woman who used my friends "6.5 Nosler" long range rifle to get t done.

Not so long ago,we common did not have smart phones with ballistic apps,Kestrels,Doppler chronographs,We didn't quite know what A Ballistic Coefficient" was good for
The "Long Range Shooter" with his 3000 +fps Weatherby was still using the same solution they used in the 300 gr 45-90 Express load. Flat shooting!

We've moved beyond the Express rifle. Shooters are far more technical today. Far more capable. And they know a new language.

Reloading has moved on,too. Just look at a rigged out Dillon 1050,with auto feeds ,a case trimmer and vacuum,a primer pocket swager…

And folks want their expensive and prepped brass to last more than 4 loadings.

The common shooter today is far beyond the common shooter of 10 years ago,.

The note SAAMI put up with the glossary indicated SAAMI recognized the need for "Shooter language" to grow with the shooting public.

Sure,technically accurate language has value and needs to be preserved.

But I don't think SAAMI wants to limit or restrict shooters and handloaders from using language to share what they learn.

[pwc]

HiBC, well written, well said

[Bart B.]

From there,we adjust the die for a desired shortening of that measurement,"The Measurement with No Name" to deduce we MAY have a desired head clearance that typically exists only in our minds because we can't go inside the locked chamber to measure it. But that deduced "head clearance" is politically correct to talk about.

There are ways to determine head clearance on a chambered round using external stuff. First thing to do is remove the bolt's firing pin spring (and ejector spring if so equipped) then reassemble the bolt, rifle and chamber a primed case. There are several ways to now determine case head clearance. Hopefully easy to figure out how.

Or use a set of headspace gauges in .0010" steps to compare chamber dimension to that of cases with a Hornady LNL gauge or its equal.

If you're 72" tall walking through a doorway whose header is 74" above the floor, how much clearance to it will there be?

[Metal god]

All rounds were headspaced on the rim

OK I've got a question . If headspace only refers to the firearm/chamber how can a cartridge be headspaced in that/those contexts ? Even that is a wrong use of the word if we only think of headspace as relating to the chamber . I'd think one of the only ways to use "headspaced" in a sentence would be . "The gunsmith headspaced the chamber" referring to the gunsmith actually cutting the headspace into the chamber .

FWIW , I'm not actually arguing that point . Just pointing out yet another argument that can be reasonably made which IMO would be just as silly .

[Metal god]

There are ways to measure head clearance on a chambered round using external stuff. First thing to do is remove the bolt's firing pin spring (and ejector spring if so equipped) then reassemble the bolt, rifle and chamber a primed case. There are several ways to now measure case head clearance. Hopefully easy to figure out how.

I tried the shim stock added to the head of a NO-GO gauge method using cut pieces from feeler gauges . I found that not to be as accurate as I was expecting . I added .004 of shims which should have given me a field gauge distance . How ever my bolt would close on the shimmed NO-GO gauge but not an actual field gauge .

Since we are talking about bumping shoulders a small amount . Even that variance throws everything off and leaves doubts as to what the actual headspace was and what to size my cases . My point , most of the methods available to the average reloader is not going to produce exact transfers or measurements . This results in at least me always having to deduce some aspect of my FL or bump sizing process .

[HiBC]

Bart. I understand what you are saying.I,ve spent many years in the shop doing just this sort of thing.

I might put yhe barreled action in the Bridgeport vise,set up a dial indicator on the bolt's rear and measure end play.(assuming bolt end play exceeds head clearance. A tight bolt/receiver could be misleading)

We could juggle shims

We might even use a piece of brass with a loose primer pocket and partially seat a primer.We might finish seating the primer with the bolt face.The primer should stay high by the head clearance.Actually,if a person made one of those up,and dropped it in a Wilson Cartridge Headspace Bushing Die
On my little granite comparator stand that lives on my loading bench...I could zero the indicator on the "SAAMI MINIMUM " step,then measure how high the primer sticks up. Bingo. can put that in the die box as a reference.

That's my zero head clearance standard.Maybe not a hardened,ground gauge,but "something"

I suppose we could beef up the case by filling it with cerro-safe before seating the primer.

Generally,there is a way to do just about anything,and usually,in the shop I worked in, they pcked me for the hard ones.

But honestly I have not taken the trouble to do those things

I might be wrong but I believe if folks care enough to measure anything,they measure the fireformed case.,case head to the ring on the shoulder.

I'm talking in a reloading room in a house with the sort of tools a handloader is likely to own or could order from Sinclair,etc.In your position on the shooting team,to have access to a graduated set of .001 increment headspace gauges might be "business as usual" .Few Handloaders have that option. We have stone knives and bear skins.

If you're 72" tall walking through a doorway whose header is 74" above the floor, how much clearance to it will there be?

I can deduce there will be 2 in clearance,but I did not measure the 2 inches.

Now,if hidden in here is a clue about inserting a long rod from the muzzle, I'm listening.
Is it something about using the firing pin as a probe? Like a depth mic spindle? I can envision some ways that could be done.

Of course,Bart,if you have a trick up your sleeve,I'm happy to learn.

[Bart B.]

It's easy to measure how much a case can be moved back and forth in the chamber with a spring loaded ejector pushing on it with a lightweight wood rod pushed into the barrel pressing against the case inside bottom.

[44 AMP]

OK I've got a question . If headspace only refers to the firearm/chamber how can a cartridge be headspaced in that/those contexts ?

Headspace, used as a noun, refers to the space in the gun for the cartridge case head. With most cartridges it is not the entire chamber, only a part of it, generally expressed as the measurement from the closed bolt face to the point in the chamber that stops the case from moving forward.

Headspaced, is an adjective, a descriptor of the point on the case that contacts the chamber and stops case forward movement. A .45acp is headspaced on the case mouth. A .30-06 is headspaced on the case shoulder, and a .30-30 on the case rim.

Headspaced as a verb refers to an action performed, such as the gunsmith reaming a chamber, he is said to have headspaced the rifle.

All are correct in the proper context. Used out of context, less so.

You can call something an aquatic avian with a spatulate proboscis, but to me its still a duck.

Bumping the shoulder back .XXX is what I would call partial resizing. The full length sizer die, when installed per mfg instructions to contact the shell holder, resizes the case body below minimum specs (to allow for brass springback and still fit in min spec chambers. Back the die body out, so that the "bump back" is less, and its partial resizing. Screw the die out a little more, so that the shoulder is not moved at all, and its neck sizing.

[Bart B.]

There's many folks who call "partial full length sizing" setting the die to size part of the case neck and let the fired case shoulder move forward a bit as the case body's squeezed down. They don't mind the bolt binding a little chambering such resized cases.

And "full length sizing" is reducing all outside dimensions except length any amount. This is pretty much the industry standard.

This conundrum has lots of case and chamber dimensions that can be complex to explain and understand via this 2 dimensional medium. Live one on one with real stuff to handle and measure is best as it's 3 dimensional.

[HiBC]

44AMP:

Headspaced, is an adjective, a descriptor of the point on the case that contacts the chamber and stops case forward movement. A .45acp is headspaced on the case mouth. A .30-06 is headspaced on the case shoulder, and a .30-30 on the case rim.

And my premise is this:

The military format of listing noun first,then modifiers may be useful

Meal/Combat individual/ B-3 unit/ Ham and Lima beans

So we have the noun "Headspace" which we can check with "Gauge/Headspace /Go and Guage Headspace /No Go.

In this instance,"gauge" is the noun. "Headspace" is an adjective,defining what kind of gauge.

The armorer might "Headspace" a Browning 1919 A-6 30 cal Machine gun,or M-2 50 cal machine gun.

And I suggest we can have,by the same format:

Length/ Cartridge Case/Headspace Its a length,specific to the cartridge case,identified as the length from case head to ref datum ring on the shoulder


Some may disagree,but IMO,its clear ,specific.and something SAAMI COULD put in the glossary.

Of course,it CAN be misused.so toss me a 30 round M1 Carbine banana clip.

We get by.

I interpret "partial sizing " as a misguided half fast attempt at semi-neck sizing with a full length sizing die.

I interpret small adjustments of the die off the shellholder as refined full length sizing. with tailored head clearance But maybe that's just me.

[Metal god]

Headspace, used as a noun, refers to the space in the gun for the cartridge case head. With most cartridges it is not the entire chamber, only a part of it, generally expressed as the measurement from the closed bolt face to the point in the chamber that stops the case from moving forward.

Headspaced, is an adjective, a descriptor of the point on the case that contacts the chamber and stops case forward movement. A .45acp is headspaced on the case mouth. A .30-06 is headspaced on the case shoulder, and a .30-30 on the case rim.

Headspaced as a verb refers to an action performed, such as the gunsmith reaming a chamber, he is said to have headspaced the rifle.

I agree but noun , verb or what ever . It's been clear to me on this forum that headspace is one thing and one thing only . That's why these threads always get closed . There's always someone that insist it's there way or no way .

Based on all those closed thread , If I can't put case in front of headspace you can't put a "ed" at the end of it and then change it from a noun to a verb to a tuna sandwich .

It either is used only one way or can evolve to mean many things in there own context .

[Unclenick]

Originally Posted by Metal God

With all do respect ( and I mean that ) just because you and Guffey say it's so , doesn't make it so .

Well, that cuts both ways, of course. I see "case headspace" and "cartridge headspace" as possible to misconstrue and you don't, except maybe by newbies. I offered examples authored neither by myself nor Mr. Guffey to say chamber headspace is what is meant in at least some instances. You offered anecdotal evidence from forum participation that indicates such misconstruing is unlikely. I think that sums it up. At this point, I suggest we just let it be a matter of personal preference what to use or avoid. There's no rule on the board that it has to be one way or the other.

I'll be interested to see if SAAMI ever does anything with it and if they do, whether they come up with a different term or decide to make Hornady's usage standard. I'm an ASTM member and our standards are created the same way. Any member can propose a standard to the appropriate committee at the annual hotel conference room gatherings and the committee can decide to ballot it.

Re the gunsmiths, cutting a chamber to size is usually called "setting" or "establishing" headspace. "Headspacing on" usually introduces what cartridge surface stops against the chamber. In the chamber, that stopping surface is called the cartridge seat, so you could say "cartridge seating on" instead of "headspacing on". The only time I've heard of a chamber being "headspaced" was either in the past tense (as in "was the chamber headspaced correctly?"), or in describing setting up headspace in the variable Savage actions.

There's always been at least some variety in the descriptions because what you measure for headspace in rimless bottleneck cases has changed post-SAAMI being organized. If you look up the headspace of a .30-06 chamber in Hatcher, it is measured from the breech face to the shoulder/body intercept. Indeed, the 30-06 and other old rimless cartridges use that and have a slightly wider shoulder angle on the case than is used in the chamber, forcing the corresponding outside corner of the cartridge case shoulder to seat on the chamber rather than the slope of the shoulder. It's not easy to measure a chamber's body/shoulder intercept accurately.

SAAMI came up with the shoulder datum idea in the '30s or '40s, I think, precisely to make the measuring easier. I don't believe the military adopted it, as the blueprints I've seen don't have a datum dimension on the chamber shoulder, but the military certainly did come up with headspace GO, NO-GO and FIELD REJECT gauges. The European CIP doesn't use a datum. The datum is really only reaching its potential value when the chamber and case shoulders have the same angle, as modern designs use. The old cartridges thus have two different measurements of chamber headspace possible, owing to the gap at the shoulder surfaces left by the difference in shoulder angles. One for the cartridge and a slightly longer one for the chamber when the case clearances are zero.

Here's an interesting aside: from Forster's description, it appears their Bushing Bump die would eliminate the .30-06 (and .270 Win, for example) shoulder angle disagreement with the chamber if they make the top end of their die match a minimum chamber rather than a case shoulder angle. Upon bumping into the shoulder, it would set the old cartridge's case shoulders to match the chamber better.

[Bart B.]

I'm a bit surprised those of us believing case heads are held against the bolt face by extractors when fired haven't chimed in to this rather well behaved discussion. Head clearance is zero in their understanding of case behavior when fired.

[pwc]

What about......

If a reloader's cartridge brass is properly "case headspace" / "cartridge headspace" (choose one or alloe both) the distance from the case head to the bolt will be the optimum distance desired by the reloader, and is controlled by their brass preperation sizing process.

Any space between the case head and bolt in excess of the desired dimension is EXCESSIVE HEADSPACE and may cause brass cartridge failure.

Really, this has always been what I understood, and is a restatement of the obvious. Now, you wordsmiths, will probably redefine obvious.

[44 AMP]

The armorer might "Headspace" a Browning 1919 A-6 30 cal Machine gun,or M-2 50 cal machine gun.

I don't know about the 1919 from personal experience but I am absolutely positive about the M2, the crew sets the headspace, every time they change the barrel. (and the timing, is supposed to be checked too) The M2 headspace and timing gauges look nothing like the headspace gauges for other bottle necked cases, the are essentially flat bars of metal (think thick feeler gauge) and are unique to the M2's design.

Length/ Cartridge Case/Headspace Its a length,specific to the cartridge case,identified as the length from case head to ref datum ring on the shoulder

Interesting suggestion, but why bother including the word headspace, why not just call it head-datum ring distance and not confuse it with including headspace?

Any space between the case head and bolt in excess of the desired dimension is EXCESSIVE HEADSPACE and may cause brass cartridge failure.

Not exactly. Excessive headspace based on what the individual reloader wants? yes. Excessive by industry standards? perhaps, perhaps not. "Any space"??? unless your case is a crush fit there is always some space. Is it always enough to be dangerous? no. Could it be,? yes, but that's something individual to the firearm and the case being fired. Not a valid blanket statement.

[Bart B.]

Originally Posted by pwc

What about......

If a reloader's cartridge brass is properly "case headspace" / "cartridge headspace" (choose one or alloe both) the distance from the case head to the bolt will be the optimum distance desired by the reloader, and is controlled by their brass preperation sizing process.

Any space between the case head and bolt in excess of the desired dimension is EXCESSIVE HEADSPACE and may cause brass cartridge failure.

Really, this has always been what I understood, and is a restatement of the obvious. Now, you wordsmiths, will probably redefine obvious.

I think the term "headspace" should have the same reference points across all three items for systems whose cartridges normally seat against the chamber shoulder when fired. Their dimensions have a few thousandths spread which makes comparison easy.

Those 3 items are case, chamber and gauge.

Same for other cartridges who normally headspace on rim or belt that are resized to seat on chamber shoulder when fired to minimize case body stretching and maximize case life.

Any empty space between case and chamber when fired is clearance. New rimmed and belted bottleneck cases typically have clearance to chamber shoulder and bolt face when fired.