What does headspace do for a rifle, round, die setup, case stretch and head separatio

[HiBC]

Mr Pond

As you may recall from my initial response to you"I think I know what is coming"

This is it.

In the PM I ,mentioned muddy water.Seems that way.

Save your cutting board.Get a machine made bushing.It is best if the top and bottom surfaces are parallel,and the hole bored perpendicular to the top and bottom surfaces.

Your calipers,by themselves,cannot find the approx. .400 dia reference circle on the shoulder of the case.The sharp,square edge of the bushing can rest on it.It just needs to be a repeatable resting place for the circle.

The top surface of the bushing needs to be flat,and parallel to the circle so your flat caliper jaw can find it to rest on.


It will work successfully if it can accomplish but one thing:Repeatability.

If you can take one case,measure it 3 times without changing anything,and get the same measurement within .001 each time,you have the tool you need.

The actual measurement does not matter,so long as it is repeatable.

Measure a few samples of brass fired in your rifle.

You can leave your rifle at home.You won't need it.

You may begin by backing the die out 1/8 turn from bumped on the shellholder.

Measure the case before sizing.The Uncle Nick label picture will give you a mental idea about what .002 change looks like.

Creep the die down till,with your bushing and calipers,you can measure that your sizing process sets the shoulder back .002.Or .003.

Lock it down,check again.

Now you are there.

If you were to use a feeler gage to check the spsce between the shellholder and the die now,you will have a reference setting to begin with next time.

Still,verify the actual change of .002 with your bushing.

I can assure you,if you follow this process,it will work.There are other processes that also work.Example:RCBS Precision Mic.It costs money,but its a good tool.

Now,re-read this post,envision the steps.Most of it,if not all,agrees 100% with what the more helpful voices here have offered.I have attempted to filter out the muck of ego and the struggle for remaining relevant

And now,Mr Pond,"Q Branch" has provide what you need to be successful

Dun da da dun dun da da da Dun da da dun dun da da da doo doo,do do do...

[Bart B.]

Good post, HiBC.

[HiBC]

Thanks,Bart!

[Pond, James Pond]

And now,Mr Pond,"Q Branch" has provide what you need to be successful

Dun da da dun dun da da da Dun da da dun dun da da da doo doo,do do do...

I second Bart B's assessment!! Nice post!

Now, if Q Branch can see to it that I get a pocket sonar shaped like spent primer cap, there is still hope for those muddy waters.

Re making my own "caliper adapter", I may still have a go, just because I like making stuff (converted the back of my van into a "sleeps 3" folding bed with breakfast table on Friday!! Only took 46yds of wood to do it. ).

I could also glue a slim 10mm washer to the board surface to give me that perpendicular edge. If I make it, I will take measurements turning the same case through 45 degrees to see if the hole was drilled straight.

[HiBC]

Do you have a carbide sizing die for your 9mm?Or maybe your 38?As decap and bell are a seperate step,the die should lack a spindle.Use the carbide sizing ring on the shoulder of your 308,and measure over the die body.It may be a bit clumsy,but it should work.

[Jim243]

That's the first time I've heard of that being headspace. I cannot grasp any logic behind this claim.

It is definitely not the space between your ears, but the space between the Head of the case and the bolt face. Take a casting of your chamber every 200 or 300 rounds and then tell me your head space is not growing from flame cutting, and I will tell you, you are full of it.

Jim

[HiBC]

Jim

Studying your post and trying to understand....

I do get it that powder gas erodes the throat and the leade in the bore

And,in a .243 the throat may detectably move forward after 300 rds,and a chamber cast would show that.

Just to clarify a term,do you consider the case "head" the end with the primer pocket in it?The part that rests on the bolt face?

I have heard folks refer to the bullet as the "head" or "bullet head" as it sits on top of the neck.

If I apply that meaning to your comments it makes perfect sense to me.

We may be talking about two different things.

[Bart B.]

Jim, here's SAAMI's definition of headspace terms as stated in their glossary:

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.

What's the difference between them and yours:

It is definitely. . . the space between the Head of the case and the bolt face.

Why is SAAMI's definition of the space between the head of the case and the bolt face called:

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.

How does burning powder erode away the chamber anyplace behind its neck where cases stop against from firing pin impact (the headspace point, shoulder, belt or rim) when it never touches that area?

I do know that the leade erodes away from burning powder at high pressure and a given match of ammo will have its bullets jump further to the eroded lands as more rounds are fired. But that doesn't change where case shoulders or belts stop the forward movement of the case from firing pin impact where they headspace at. This is the inconsistancy I see in your headspace definition. And it's contradicted in your comment:

It is definitely not the space between your ears, but the space between the Head of the case and the bolt face. Take a casting of your chamber every 200 or 300 rounds and then tell me your head space is not growing from flame cutting, and I will tell you, you are full of it.

Throat erosion from firing is a long ways forward of where head clearance is between the bolt face and case head that exists when the round fires. There's no "flame cutting" between the bolt face and case head.

I, like HiBC, have also heard folks refer to the bullet as the "head" or "bullet head" of a cartridge.

[F. Guffey]

They are not sloppy at all when correctly used.

Bart B., Jim Watson was not talking about the methods and or techniques, his reference to 'loose at best' was the threads on dies and in presses. An experienced reloader knows to remove the slack between the threads, to do that there is no better way than 'the feeler gage, the companion to the press.

Regardless of method and or technique a reloader needs to learn the value of verifying, make an adjustment then verify, or use the verifying tool the feeler gage to make the adjustment, then there is no reason to verify.

Jim Watson, with the slack removed I can use a height gage to measure the die height above the press, it helps to have a decent understanding of zero, screw the die down to the shell holder, zero the gage then back the die out .001", I have one chamber I load for that requires I back the die out .014". I use 280 Remington cases for that 30/06 chamber because the additional length of the chamber is between the shoulder and bolt face.



F. Guffey

[F. Guffey]

Quote:
That's the first time I've heard of that being headspace. I cannot grasp any logic behind this claim.

It is definitely not the space between your ears, but the space between the Head of the case and the bolt face. Take a casting of your chamber every 200 or 300 rounds and then tell me your head space is not growing from flame cutting, and I will tell you, you are full of it.

Jim

Head, a term used to identify a bullet, not a common term used is the USA.

F. Guffey

[Bart B.]

I thought the best, simplest and easiest way to remove the vertical slack between the die and press threads was to tighten the die's lock ring hard against the press when the die was set to the right height. What other reason is there for die makers to supply that lock ring? They even tell you to do it.

Slipping a feeler gauge between a case head and shell holder face does nothing to eliminate the space between the die and press threads caused by their dimensional tolerances. The difference goes to zero when the case starts into the die whether there's a feeler gauge in the system or not. That feeler gauge only pushes the case a bit further up into the die after all the slack/slop/space between the die and press threads has been reduced to zero. If the die's locked hard against the press with its lock ring, there's no vertical slack/slop/space between the die and press threads with or with out anything atop the ram be it shell holder, gauge or anything, including ones finger if they're clumsy, and case. The die's position in the press is fixed.

An experienced reloader knows to remove the slack between the threads; he tightens the die's lock ring.

[Jim243]

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

Bart, if you actually took the time to read my posts, that is exactly what I said in post #37. Also why are you mixing apples and oranges, the head space relates to the rifle not the case. The base part of the case is refereed to as the head, but that is not what we are talking about.

F. Guffey, as you fire your rifle both the gasses and friction of the bullet will cause erosion of the throat and chamber and yes even that part of the chamber that the shoulder indexes on. As that continues the chamber will elongate to the point that even a properly set shoulder and case will move forward in the chamber increasing the "Head Space" to a point that you can close the bolt on the "rifle" even with a "no-go gauge" in it. At that point you have excessive "head space" when you can close the bolt easily with a no-go gauge inserted in the chamber.

I shoot 243's and I should be good for 750 rounds before the barrel needs to be replaced. Those that shoot 308 are good to around 5,000 rounds. If you shoot wildcat rounds like 6mmbr or 260's, or 222's the erosion is faster than other standard calibers.

This concept should not be this hard to understand.
Jim

[Brian Pfleuger]

This concept should not be this hard to understand.

It's hard for me to understand because in all the years I've been on this forum it is the first such claim I have ever heard and it is contradictory to every thing I know about what happens in the gun.

In other words, if your bottleneck cartridges headspace is getting longer, you are stretching the action/recoil lugs. It is not because of flame cutting as there is no flame (none whatsoever) in contact with the areas related to headspace.

[Jim243]

you are stretching the action/recoil lugs.

That's the first I heard of that. I have heard of flame cutting the bolt from punctured primers.

Jim

[Bart B.]

Jim, on two rifles chamberd for the .308 Win and both originally had chamber headspace at 1.630", they were swapped in and out of one receiver for about 3000 rounds each. Chamber headspace never changed over the life of the barrels. Fired case headspace remained at 1.629" from both for the 3000 rounds fired in each. Nor did the bolt face position relative to the barrel tenon's shoulder where it stopped against the receiver face. Both barrels' throats eroded their lengths about 1/10th inch over their life. So, bullets needed to be seated shallower in case mouths. The full length sizing dies never had their lock rings' position changed so they sized fired cases back to a headspace of about 1.628"

In today's rifle jargon, headspace also refers to the distance from case head to some diameter on the shoulder; typically the same one used to reference the chamber shoulder it abuts against when fired.

In your post 37, it says:

The sad truth is that every time you fire your rifle you are changing your head space, not by much, but you are fire cutting the throat of your chamber each and every time. Like I said it is not by much, but after thousands of rounds the chamber will no longer be in spec to the caliber you are shooting and it will be time to replace that barrel with a new one.

That's what my remarks were relative to. Fire cutting erodes away the leade, or throat increasing its distance/space from the chamber/case mouth. However, if you're calling the bullet the "head," then yes, the space it travels for a given lot of ammo assembled to the same OAL, will change. If you "chase the leade" as I did seating bullets out further as the throat eroded, then that "head space" doesn't change; especially when bullets are seated such to seat .010" deeper in the case when chambered. That keeps that "head space" at zero for every round fired, regardless of where the leade's at.

Normal loads in soft steel actions has been setting bolt lugs forward (or receiver lugs back) for decades. This was the problem with some of those low numbered Springfield M1903's, but not all of them. Some Mauser 98 ones had the same problem. And the early British double rifles were only good for working pressures of about 40,000 cup (SAAMI's spec for the .470 Nitro Express). Higher pressures from factory bolt action ammo at 55,000 cup were tried in rebarreled double rifles only to learn that their massive breech was bent from that much pressure. 'twas called "breech set back' as I remember.

I know people who've worn out several .308 Win. barrels all fitted to the same reciever and bolt combination. I've got one myself. Their receiver face to bolt face dimension never changed. Proof to me that with safe, maximum loads, bolts and receivers hold their dimensions quite stable over many dozen thousands of rounds. Which totally discredits the following:

...as you fire your rifle both the gasses and friction of the bullet will cause erosion of the throat and chamber and yes even that part of the chamber that the shoulder indexes on. As that continues the chamber will elongate to the point that even a properly set shoulder and case will move forward in the chamber increasing the "Head Space" to a point that you can close the bolt on the "rifle" even with a "no-go gauge" in it. At that point you have excessive "head space" when you can close the bolt easily with a no-go gauge inserted in the chamber.

[Brian Pfleuger]

I have heard of flame cutting the bolt from punctured primers.

I've heard of guns blowing to pieces. Are we talking about extreme events unrelated to any normal condition?

I suppose we are, actually, because what you describe only happens at extreme pressures high enough to stretch the action/bolt lugs.

[Jim243]

http://odcmp.com/Sales/askarmorerheadspace.htm

[Bart B.]

Every time I fire my rifle I'm changing the rifle's bolt face to shoulder dimension?

What's the average amount head space changes per shot as the bolt face and/or receiver lugs move back or the chamber shoulder and/or the bolt lugs moves forward; both if at the same time? Unless you've got some numbers to back up your claim, I think you're making assumptions based on your own perspective as to what happens when a round's fired.

Having observed chamber shoulder areas of barrels with several thousand rounds through them, I've never seen any evidence of erosion by any means on the shoulder area. If there was, it would be part of the "fingerpring" left on case shoulders when fired in addition to normal machining marks.

If high presure gas cutting really did eat away the steel chamber shoulder, how come nobody's ever mentioned seeing gas cutting on that much softer, more easily melted metal that gas also has to move against as it seals the barrel preventing gasses blowing back into shooter's body parts? Brass case shoulders, and necks, too, for that matter.

[F. Guffey]

F. Guffey, as you fire your rifle both the gasses and friction of the bullet will cause erosion of the throat and chamber and yes even that part of the chamber that the shoulder indexes on.

and then the last part

This concept should not be this hard to understand.

"as you fire your rifle" I have am exemption or it is another one of those things that is not fair, it does not happen to me. I have no less than 60 take off barrels, some have been fired from thousands of times to thousands upon thousands of times. I do not turn shot out barrels into tomato stakes. I cut the chamber from the barrel and turn them into chamber gages, the cut off portion of the barrel can be cut and turned into chamber gages.

I do not have a take off barrel or a cut off chamber that has damage to the chamber and or neck portion of the chamber.

I do not have an infatuation with head space, for me it is much more simple, I deal with the length of the chamber from the shoulder to the bolt face. A concept that must be impossible to understand.

F. Guffey

[HiBC]

When I built my 257 AI on a Mex Mauser receiver,I used a Yugo bolt.There is a little length thing to compensate for with an extended barrel shank,and an extractor notch is required.I lapped the lugs to good solid bearing on each.

I chambered it so I could just feel the "Go" with the stripped bolt as it closed.Not crunch,just feel.

I built two of these,one for a buddy.We began loading 100 gr Sierra boat tails pushed by IMR 4350.I was younger and less prudent then.The man with the Oehler 33 said I was getting 3400 fps.I won't post or recommend the load.

Primer pockets stayed good till necks split.

We burned an 8 lb can of powder.Thats about 500 rds per rifle.I cleaned it,stripped the bolt,and put the same headspace gage back in.I was checking for lug setback,not chamber erosion.

There was no perceptible change.I could still just feel the gage.

My initial load with the brand new,just out! Nosler 115 Ballistic Tip (a while ago) chrono'd 3150.H4831sc,and not in the book.Douglas fwt bbl and it still puts them in the orange diamond at 300 yds.Several years ago I did back off to 3050 fps...just seemed wise.

I'd believe the throat is worn,but the chamber is not.This rifle was built 20 +years ago.

[Metal god]

Jim

These rounds were just fired last week . They are shots 2030 through 2034 fired from my rifle . They are also the 1100 shots fired since I started measuring the case head space of cases fired from this rifle . They measured exactly the same as the first time I measured my cases 1.623"


Here is a link so you can zoom in and take a close look . I marked the area on the center case where my comparator sits . You can see the mark on the others . These cases have been reloaded 7 times .
http://imageshack.com/a/img842/1931/4ehk2.jpg

As you can see these cases completely seal the chamber from breach to top of shoulder . Where does all the gases come from that are eroding the datum line/shoulder of my chamber . I should also ask if the 243 noticeable erodes this area after 300 rounds . Is 1100 308 rounds enough to show the erosion you claim is going to happen ?

[Pond, James Pond]

Save your cutting board.Get a machine made bushing.

I may still, but for now the cutting board had it coming.

I now have a 50mm washer with a 10mm hole, superglued on to a 50mm disc of cutting board, replete with 10mm hole through it!

Let's see if I get consistent readings!!

[HiBC]

Have fun,but remember you have a 9mm or 38 spl sizing die with no spindle in the way.Its the right size,just a bit long.If you open a vise about 1 cm,lay the die across the jaws and clamp gently on the lock ring,you will have one hand for the cartridge case,and one hand for your calipers.No additional appendages should be necessary.

[Jim Watson]

Yes, Bart, I know about the die lock ring.
That does not make the die easier to adjust.
I still think there could and should be an easier way to adjust the sizing die than tweaking it in its body threads. Most seating dies do. Not all, I routinely curse Dillon every time I change a 9mm load, being too cheap to pay the price of a micrometer seating die for bulk pistol ammo.

That said, I will probably print out some Unclenick lockring protractors to simplify sizing die adjustment. Hmm, guess I can put one on that Dillon seating die, too.

[Jim243]

Jim

These rounds were just fired last week .

WOW NICE cases, I wish mine came out that clean right from just being fired and you don't even have to trim them, that's great.

Well it's time to stop arguing with you all, so I guess I will have to agree, YES the earth is flat.

Jim