Where's Case Head When Round Fires?

[F. Guffey]

Yes, numerous times you have said that. However, you have never once explained how? I am sure, myself among them, inquiring minds would like to know how so please do explain exactly how you can do that three times without the use of a hard space gauge?

Amd then Bart B. has made claims the case shortens between the shoulder of the case and case head when the firing pin strikes the primer. He has claimed he had old friends that have claimed 'it is so'.

I have tested 'failed to fire ammo that had been had been struck 3 times in one rifle and 4 additional strikes in 4 additional rifles. It was not a miracle, the case did not get shorter with all of those heavy strikes. I wanted nothing to do with it but the ammo came to me that afternoon, I suggested they call Remington, the phone number was on the box.

I pulled the failed to fire ammo down and checked the components, nothing; I then reinstalled the primers and then chambered the cases with the primers and fired each one with a heavy blow of my killer firing pin.

I then measured the length of the case from the shoulder to the case head and found the case did not shorten from the shoulder to the case head.

All of the tools I used were home made. When the ammo was brought to me they included new unfired ammo from a box of unfired ammo, they brought me 15 cases that had been fired in a new rifle and they brought me the 5 failed rounds.

there was not .0015" difference in length between all 20 rounds/cases. And I was thinking the chamber in that new rifle had to be on the minimum length size.

F. Guffey



All 5 failed to fire primers fired. And it was not a miracle, with the heavy strikes of my firing pins none of the cases shortened due to the impact of the firing pin.

[F. Guffey]

One of my tests.... New Federal nickel plated 308 cases had their shoulders set back .008" with 38 grains of IMR4064 under 165 grain bullets. Primers were backed out about the same amount. New brass cases loaded the same had .004" shoulder setback.

Straight away: He is claiming the shoulder set back after I insisted it is impossible for the shoulder to move. There is no way to understand the problem because the shoulder does not move.

I have said I have formed cases that shortened .035" from the end of the neck to the case head. And then there is the 'while the case got shorter' thing the case got longer from the shoulder to the case head. for a reloader that has got to be a mind boggling thing. The came cases that shorten .035" shortened an additional .010" when fired and again: the cases did not shorten from the shoulder to the case head, they shortened from the end of the neck to the case head. I do not believe it but some of this stuff could only happen to bump reloaders, you know those are the ones that a sentence with "I bump my shoulders back…"

F. Guffey

[cw308]

Bart B
There is no pressure on the case from the plunger, I could have left the plunger out but didn't like the idea of grime building up in the tunnel . Fired case lays in the follower , I like it that way , no need to chase my fired cases .

Chris

[Reloadron]

Mr Guffey all I asked you was:

Yes, numerous times you have said that. However, you have never once explained how? I am sure, myself among them, inquiring minds would like to know how so please do explain exactly how you can do that three times without the use of a hard space gauge?

Your response was:

Amd then Bart B. has made claims the case shortens between the shoulder of the case and case head when the firing pin strikes the primer. He has claimed he had old friends that have claimed 'it is so'.

I have tested 'failed to fire ammo that had been had been struck 3 times in one rifle and 4 additional strikes in 4 additional rifles. It was not a miracle, the case did not get shorter with all of those heavy strikes. I wanted nothing to do with it but the ammo came to me that afternoon, I suggested they call Remington, the phone number was on the box.

I pulled the failed to fire ammo down and checked the components, nothing; I then reinstalled the primers and then chambered the cases with the primers and fired each one with a heavy blow of my killer firing pin.

I then measured the length of the case from the shoulder to the case head and found the case did not shorten from the shoulder to the case head.

All of the tools I used were home made. When the ammo was brought to me they included new unfired ammo from a box of unfired ammo, they brought me 15 cases that had been fired in a new rifle and they brought me the 5 failed rounds.

there was not .0015" difference in length between all 20 rounds/cases. And I was thinking the chamber in that new rifle had to be on the minimum length size.

F. Guffey

All 5 failed to fire primers fired. And it was not a miracle, with the heavy strikes of my firing pins none of the cases shortened due to the impact of the firing pin.

I am not concerned with Bart B. I just wanted to know how you measure a chamber without a headspace gauge. Simple enough question. So what I read is you use some home brew gauge which is of no help to anyone here. So less a headspace gauge anyone here can't measure a chamber headspace. Would that be it in a few words?

Ron

[Metal god]

He will never explain him self . He knows to much to need to explain anything to us guys that have not a clue about anything reloading . Trolls never need to explain , that’s not the purpose of there participation . They never want to help , only antagonize . Sad really when you think about it .

[cw308]

Where's the case head when rounds fire ? If your sizing with .001 of case space and the case stopping at the shoulder , my way of thinking , it would be .001 from the bolt face.

[Reloadron]

This forum needs a like button, a quote button would also be a nice touch.

Ron

[tangolima]

The very same question has been asked more than twice (that I know of) on this forum. Same arguments (killer firing pin and all that) by exactly the same characters (myself included). Are we really running out of things to do?

I'm not going to repeat what I said before. Just really quick. I have toiled to size my brass to have 0.002" to 0.004" head clearance. I simply refuse to agree the firing pin strike screws it up to dangerous level of 0.007" or more. It is too depressing.

Good day, gentlemen.

-TL

Sent from my SM-G930T using Tapatalk

[F. Guffey]

Yes, numerous times you have said that. However, you have never once explained how? I am sure, myself among them, inquiring minds would like to know how so please do explain exactly how you can do that three times without the use of a hard space gauge?

Inquiring minds would like to know: If I could find a way to make it your ideal or Bart's IDEAL it would be a 'done deal'. Again Bart B. claims he can determine where the clearance is located. At the same time he declares those that believe it is between the case head and bolt face are wrong. It is not an opinion, I know for a fact checking clearance between the case and chamber requires a minimum of skill.

It does not disturb me that Bart B. makes the claim of being the expert on case location in the chamber. It does not disturb me that you do not place any demand on him to explain "how he does that". But I can determine where the clearance is located and at the same time determine the difference in length between the chamber and case from the shoulder to the case head and bolt face.

My cases do not have head space, Bart B. had a lot of time invested into the ideal the case had head space. And then one day he found SAAMI did not list head space on their case drawings. There was no way I could make it his ideal so he called SAAMI. I am sure they were impressed, I have not found any changes in the way SAAMI list information on their case drawings. I thought it was a matter of learning to read a map and or scope. I do not know how anyone can read a map without a legend; SAAMI does not use the symbol for head space in their case drawings. I accept that because there is nothing about my ego that demands I claim I am correct.

Again: I have insisted it is impossible to move the shoulder back with a die that has full length sizing capabilities. I have insisted t is impossible to bump the shoulder back for the same reason. I know, you hate to hear this but I am the only reloader that can not move the shoulder of the case back with a full length sizing die that has case body support. I no longer wait for someone to explain how they move the shoulder on a case back with a die that has case body support.

I would like to give you credit for something, in my opinion it would not hurt me to do that but you will have to earn the credit.

F. Guffey

[F. Guffey]

Where's the case head when rounds fire ? If your sizing with .001 of case space and the case stopping at the shoulder , my way of thinking , it would be .001 from the bolt face.

I do not agree but now you have to find out from Bart B. where the transition is. And then have to determine what action is being used. And then forbid there are controlled feed and push feed actions. And then? And then?

I fired 8mm57 ammo in an 8mm06 chamber. The difference between the length of the case from the shoulder to the case head when compared to the chamber is .127". I should not have to type slowly but if the clearance was located between the bolt face and case head the firing pin would miss the primer by .075".

Therefore: The clearance was not located between the case head and bolt face. And then there is that thing about the firing pin driving the case forward The results would have been the same had my chamber had no shoulder, the shoulder could have gone out to infinity.

AS it was I had just enough case to for a new shoulder, no, the shoulder on my case did not move, it was erased when it became part of the case body. I know you wonder about the shoulder of the case that was formed when fired; the new shoulder was formed from part of the old shoulder and neck.

Because of all the forming the case was ejected with only a hint of a neck.

F. Guffey

[5whiskey]

Interesting topic, as well as some of the discussion.

JMorris thanks for the video. I do believe that is, in fact, one way it can go. I also believe there are chambers tight enough to offer sufficient resistance so that the case does not move forward when struck by the firing pin.

I also do not believe that anyone here has a system of real time measurement of a fired case. Simply measuring case stretch doesn't tell anything other than the case stretched, either by the shoulder moving forward or the head moving rearward. I suppose a witness mark can be induced midway of the case to then measure in both directions, but when measuring in the thousandths I would question the ability to accurately and repeatedly measure from the exact same spot. I know, for fact even, that thrice-fired neck-sized ammo fired in the same chamber will offer resistance to the bolt on closing. Because of this, I contend that there is no way that the case head can come off of the bolt face upon firing. There simply isn't room to. I also believe that there are chamber/ammo combinations loose enough so that the case head comes off of the bolt face at firing (or even before firing and stays off the bolt face during firing). I understand the premise, I believe, of the question to pertain to SAAMI spec commercial ammo in an off-the-shelf rifle chamber. In those cases, I think the answer is... it depends.

[F. Guffey]

I also do not believe that anyone here has a system of real time measurement of a fired case. Simply measuring case stretch doesn't tell anything other than the case stretched, either by the shoulder moving forward or the head moving rearward.

It would be nice if I had the luxury of disagreeing, if I did I would disagree. I have no hang-ups about the shoulder of the case, reloaders have an enfaucaction with the moving shoulder when sizing and firing, I don't but I am not the one that jumped into the middle of this deal; remember I am the one that finds it impossible to move the shoulder back with a die that has case body support.

F. Guffey

[jmorris]

JMorris thanks for the video. I do believe that is, in fact, one way it can go. I also believe there are chambers tight enough to offer sufficient resistance so that the case does not move forward when struck by the firing pin.

I also do not believe that anyone here has a system of real time measurement of a fired case. Simply measuring case stretch doesn't tell anything other than the case stretched, either by the shoulder moving forward or the head moving rearward. I suppose a witness mark can be induced midway of the case to then measure in both directions, but when measuring in the thousandths I would question the ability to accurately and repeatedly measure from the exact same spot. I know, for fact even, that thrice-fired neck-sized ammo fired in the same chamber will offer resistance to the bolt on closing. Because of this, I contend that there is no way that the case head can come off of the bolt face upon firing. There simply isn't room to. I also believe that there are chamber/ammo combinations loose enough so that the case head comes off of the bolt face at firing (or even before firing and stays off the bolt face during firing). I understand the premise, I believe, of the question to pertain to SAAMI spec commercial ammo in an off-the-shelf rifle chamber. In those cases, I think the answer is... it depends.

I agree except I think one could be able to see what happens during firing with the right equipment.

Not unlike 6:58 into this one. You get a glimpse into what’s really happening the instant before things get destroyed.

https://www.youtube.com/watch?v=7pOXunRYJIw

[Bart B.]

I would like to see 308 case headspace measurements before and after across 15 shots starting with a max load then 1% progressively less by someone reading this thread. If max load is 45 grains, each subsequent load is .45 grain less. And measure primer push out from case head on each one. Ensure bullets have at least .020" jump to the lands and use full length sized cases with a couple thousandths head clearance.

If you cannot figure out how to do this, PM me and I will help.

[F. Guffey]

If the case had head space? My cases do not have head space, I use the length of the case from the shoulder of the case to the case head to off set the length of the chamber.

And then there are short chambers. Short chambers? Still not a problem; RCBS shell holders afford me the luxury of shortening a case from the shoulder to the case head .010"

F. Guffey

[stinkeypete]

Forgive me for being the noob here- I’m confused.

1. I don’t want to resize the shoulder, do I? I am just resizing the neck because bolt rifle and fire formed brass. What am I missing?

2. Shoulder moving because of firing pin force must be very small for fire formed brass. It seems one could make a solid brass dummy primer, cast a cross section of a dummy round in plaster, remove the dummy round and fire it and then compare it. Smack the primer a few times, compare.

I can see a problem if the shoulder is not (nearly) touching the chamber in that the case will stretch.

3. You guys are many years ahead of me. I don’t even understand what you are talking about and I have a degree in physics.

4. Rimmed cartridges, straight walls... way easier. Still not simple.

[HiBC]

stinkypete….You get to decide what to engage in,and what to just ignore.

I don't try to understand the thought process of a dog barking at a squirrel.Its a waste of my time and energy.

Bart B posed a question he knew the answer to to spark a good discussion,and to get some of us to think,imagine,watch the cartoons in our head.

I don't know Bart B,personally,and I don't know his resume. I think it includes something about being a world class Palma competitor who shot for the US Navy. I think maybe that means the US Navy resources were available to test and develop what works and what does not. For most of us this stuff is a hobby.I think maybe Bart B was in a position it was more than that.

This has been a good discussion.

Eventually the barking dogs and egos show up. The intelligent,useful discussion ends,and it becomes more like listening to party politics and news media talking heads. You can follow it,make your head hurt but it becomes less worthwhile.

Over time,you will learn what is just not worth even reading.Its just irrelevant noise,and its been the same record skipping over the same groove saying nothing useful for years.

Welcome back,Bart B !! You are good to have around.

Thank you for giving us a few shovels of rich ore to pan for any nuggets we might find. Its been good,and I thinh a lot of folks can watch what happens in their mind now.
That's how folks learn.At least,some do.

[jmorris]

Mr. B could be the most knowledgeable person on earth. He could also help the other idiots on earth by enlightening all of us.

That doesn’t seem to be the goal. Cartoons are fantasy, if you can share knowledge, share it. Discussion is fine but without support for your data it’s not far from BS.

He has been asked how he arrived at his conclusions and even asked for others to try to duplicate his results.

I would like to see 308 case headspace measurements before and after across 15 shots starting with a max load then 1% progressively less by someone reading this thread.

Even a 5th grade science student would know to follow the scientific method and have standards for testing but the only one here that has a clue to what he did exactly, is himself.

We could follow in his foot steps if he gave us any information on how he gathered the data he has posted but that doesn’t seem very likely at this point.

[jmorris]

May be the same Bart B. From a thread in 1994.

https://groups.google.com/forum/m/#!...ns/neQOfipj5oI

How much lower? Ever measured it? Ever done a model using diagrams
of chambers and cases to see how much lower they set? What if the ejector
pushes the bullet off to one side, too; ever consider this situation that
always happens when ejector is pushing on the edge of the case head that
is opposite the extractor (as most centerfire actions are these days) and
forcing the loaded round to not even lay at the bottom of the chamber in
the first place?

Followed by Cases tend to produce the best accuracy after being fired about 3 times.

Because their case head is now very square with the squared-up bolt face
which means it impacts evenly around the bolt face with each firing. For
bolts whose face is not trued up square with the chamber axis, this doesn't
apply; none of the cases will ever fit correctly when fired. As the high
point of the off-square case head impacts the high point on the unsquare
bolt face, the barreled action starts whipping in a different direction
and that causes the bullet to exit the muzzle at a different place making
it not shoot to group center but some distance from it. Many tests have
been done to prove this very thing.

And another saying

(That's deliberately vague, I'm not getting into a debate
on statistics.

Wise words, kind of like me when my wife asks me how a pair of shoes look....

[Bart B.]

Consider the following situation......

You have full length resized your fired rimless bottleneck cases such that case necks are perfectly centered on the shoulder. The necks are also well centered on the case body axis. Thanks to the sizing die keeping these case parts aligned on one axis; neck only dies don't do that. After priming, charging and seating bullets, you measure bullet runout. All reloaded rounds are very straight and maximum runout is less than .001 inch. Their outside dimensions are .001 to .002 inch smaller than that of the chamber.

When the round fires, you want the bullet to be as perfectly centered in the barrel as possible.

When chambered and the bolt closed in battery, the case body back end at its pressure ring is usually pressed against the chamber by the extractor force. The back end of the round is a tiny bit off center in the chamber, but it is very repeatable across all rounds

What must happen to the case to best center the bullet in the barrel before the round fires?

[Bart B.]

Originally Posted by jmorris

Mr. B could be the most knowledgeable person on earth. He could also help the other idiots on earth by enlightening all of us.

That doesn’t seem to be the goal. Cartoons are fantasy, if you can share knowledge, share it. Discussion is fine but without support for your data it’s not far from BS.

He has been asked how he arrived at his conclusions and even asked for others to try to duplicate his results.

Even a 5th grade science student would know to follow the scientific method and have standards for testing but the only one here that has a clue to what he did exactly, is himself.

We could follow in his foot steps if he gave us any information on how he gathered the data he has posted but that doesn’t seem very likely at this point.

I think what I posted was clear enough. If not, you first need to detail strip your rifle then learn how each part's fit and function changes case fit to chamber using a primed dummy round. Then get or make a case headspace measuring device then learn how to use it. Otherwise, understanding exactly what I did would not be understood.

[jmorris]

When chambered and the bolt closed in battery, the case body back end at its pressure ring is usually pressed against the chamber by the extractor force....

I think what I posted was clear enough. If not, you first need to detail strip your rifle then learn how each part's fit and function changes case fit to chamber using a primed dummy round.

I grabbed the bolt in #34 and a dummy round, the extractor doesn’t have any force on the case at rest (unlike a 1911 for example). Mine doesn’t seem to function the same as yours. Maybe why we have different realities.

[Bart B.]

Originally Posted by jmorris

I grabbed the bolt in #34 and a dummy round, the extractor doesn’t have any force on the case at rest (unlike a 1911 for example). Mine doesn’t seem to function the same as yours. Maybe why we have different realities.

How much maximum clearance from bolt face to case head is there with that bolt?

Does the extractor hold an empty case in the removed bolt?

How much shorter is your loaded case headspace from chamber headspace?

[Don Fischer]

Originally Posted by Metal god

It's a good question because Bart did not give a reason as to why he asked a question he already knew the answer to .

I'll answer both , It matters A LOT ! ok that's one question answered , now for the why .

To know what is and what causes case head separation .



These cases were only reloaded 3 times . The problem was I was bumping the shoulders .008+ from fire formed from the same rifle that shot them . This resulted in excessive head clearance or the very thing we are discussing here . A large space ( in reloading circles ) left between the case head and bolt face when fired . This caused the cases to stretch in the web area more then you ever want . After stretching that extra amount 3 times the cases failed .

So why does the question matter . For me , to understand what's going on when you say internal ballistics .

That ring around the head is not caused by any gap between the bolt face and base of the cartridge. It's caused by the gap between the shoulder and it's bearing surface in the chamber. What you see if known as excessive headspace and can normally be overcome with partial FL sizing!

When the firing pin hit's the primer, the cartridge is pushed forward a bit. If it is pushed to much it will possibly not set off the primer, nothing more than that. Without firing that start of case head separation you see will not happen. When that does happen it the distance of the shoulder to it's surface in the chamber. Fire the round and usually the case is pushed forward just a bit millisec's before igniting the primer. When the primer ignite's the pressure starting to build push's the whole case backward to the bolt face. As pressure increase's, the case shoulder moves forward pulling from behind it. The head is solid and won't pull so the only place it can pull from is a point right in front of the head, just where you see it in these pictures. A clear indication of excessive head space. Normally the problem can be overcome by simply partial FL sizing the case so that the sized case fit the chamber you have. I partial size for every rifle I own. I have two 243's and the ammo from one will chamber in one but not the other. The ammo in the other will chamber in both. Nothing more than a difference in headspace. Having more headspace is not necessarily bad nor will it start the separation you see in the picrute. What cause's that is excessive headspace. Fire factory ammo in that rifle the first time, new stuff never reloaded and I suspect you will not see that separation starting.

That start in separation isn't normally seen in rimless cartridge's. It's usually seen in cartridges that don't headspace on the shoulder, Rimmed cases and belted case's generally. Reason being headspace on other than the shoulder leaves the chance of a sloppy chamber, one where the cartridge has to stretch to much to stop the stretch of the case. I've never seen it happen with new case's, only reloads and then only after several time's fired.

The base of the case moving away from the bolt face is no problem other than the round may not get enough force from the firing pin to fire the round. In that case, I doubt the case can move forward farther than the extractor, headspace has no issue here. There are a lot of guy's that like to size so they can feel the shoulder rub in the chamber a bit. That has nothing to do with the primer pocket or movement of the bolt. Other's like to seat the bullet a bit into the lands. Again nothing to do with the relationship of the bolt face and the base of the case, but, can play h*ll with pressure!

[Bart B.]

Originally Posted by Don Fischer

That ring around the head is not caused by any gap between the bolt face and base of the cartridge. It's caused by the gap between the shoulder and it's bearing surface in the chamber.

I don't agree. Most common cause is case shoulders bumped back too far when resizing cases. Case shoulder is hard against chamber shoulder and case expands back stretching case body at the pressure ring.