Hi Guys

Can anyone explain to me how the process works for measuring case head expansion to find the maximum load for a particular rifle when developing loads. thanks

Run a search for CHE with Hot Core as the author.

thanks Ol'Joe

This may explain it better
http://www.jamescalhoon.com/primers_and_pressure.php

Hey Oscarhans, Here is a link to measuring CHE & PRE. If you follow those instructions, you will have the best possible Pressure Indication Method available for you. If you do something other than what is listed, then you are on your own.

CHE is a good indicator for most cartridges including Wildcats. It is not useful on older low Pressure Cartridges because the Case head will not Expand at their SAAMI Pressures. And some Case designs require a Thin Blade Micrometer to attain the readings.

PRE works on every Case ever made once you have a Standard to compare it to. It only becomes useful on Wildcats after the SAFE MAX Pressure is determined by using CHE. Then you can also use it there.
-----

There is a lot of information available on the net concerning how to do CHE & PRE measurements and most of it is based on misconceptions, has flaws or is simply wrong. I've used the above Methods for over 5-decades and if they are followed exactly as written, they will work fine for you.

Best of luck to you.

I have been wanting to ask Hot Core about this very thing. May I share your thread oscarhans? Hopefully, the answers to my question will help with answering yours.

I have been loading for my hornet and have developed what I thought to be quite a hot load. (It hits pretty hard anyway). Yesterday, I loaded up a new case and found what I expected - the powder reached the brim. Well, I fired it, expecting signs of a little too much pressure, but, to my surprise, the case showed signs of a mild pressure load! The primer - Federal 200 - showed a fair amount of flattening but not scary. How does one determine the pressure in a low-pressure cartridge like the hornet? The case shows very little sign of gripping and slipping against the chamber walls and case length growth is zero. Expansion at the expansion ring is visible with careful examination and measures the same as a case fired many times but is not so obvious to the eye.

quote:

Originally posted by 303Guy:
...Expansion at the expansion ring is visible with careful examination and [/b]measures the same as a case fired many times[/b] but is not so obvious to the eye.

PRE is the only way to get a Pressure Indication that is useful in Low Pressure Cartridges.

You still need to shoot a box of Factory Ammo through your rifle and Average all the PREs to establish A Comparative Benchmark Standard. Once you do that, go through "your" Load Method using those same exact once-fired Cases and check the PRE as the Load Increases.

Since you will be using a different Rifle, Primer, Powder and Bullet than the Factory did, it is not possible to predict where the Upper Pressure Limit is located without measuring and comparing the PRE to what the Factory Ammo indicated. When you do that, and STOP adding Powder when the PRE is the same as the Factory Ammo, it only tells you that you are at the Same Pressure the Factory loaded their ammo to. It does not tell you what the Pressure actually is.

In fact, there is no method or equipment available to indicate the actual Pressure outside a Certified Ballistics lab, including the totally worthless HSGS fiascos.

I have used CHE for years and bought a Mitutoyo blade micrometer and have a very good "feel" with it and believe it's accurate to about .0002" when prudently used. I believe it provides good information about when one is APPROACHING maximum pressures for the brass being used. I still rely on primer pocket expansion as the ultimate test.

Hey Hot Core.....have you found a coorelation between CHE and primer pocket expansion to any degree?.....meaning when we are .0005 growth in CHE we also are seeing some starting primer pocket expansion..... Theoretically there should be some type of coorelation...

I absolutely agree with your thoughts that there should be a correlation.

However, I've not made a definitive study of it to see how many tenthousandths of CHE results in how many tenthousandths of Primer Pocket Expansion.

If I was still working and still had access to a set of Pin Gauges, it would be very interesting to see how a few 223Rem, 30-06 and Belted Mag Cases responded.

One of our buddies uses "Groove Expansion" which is reading directly at the Primer Pocket. Perhaps he will jump in if he isn't out Hunting.

quote:

In fact, there is no method or equipment available to indicate the actual Pressure outside a Certified Ballistics lab, including the totally worthless HSGS fiascos.

Hot Core was doing well this time but he just couldn't resist with his usual remarks. He is wrong. I have an Oehler m43 and am quite able to measure factory pressures and duplicate them quite easily and reliably. I can measure the pressure of numerous loads and have a viable comparison between them. You can not do that with CHE or with PRE. I used CHE and PRE for years and always found gross inconsistancies with CHE. PRE on the other hand generally works ok to develope factory equivelent presures.

However, I do disagree with Hot Cores use of the once fired cases to develope your load in when using PRE. The psi required to expand the once fired and not sized back to original dimension cases is different than when they were unfired. The best method for PRE is to fire 5 of the factory loads and establish the average expansion at the expansion ring. Then disassemble the remaining factory rounds (including removing the primer) and develop your loads in those unfired new cases. When you have an average expansion at the expansion ring equal to the factory load's average expansion your reload's pressure will be equivelent to the factory pressure.

If you are also using a chronograph you can also judge the quality of your load vs the factory load by the SD and ES. If you can also tell if you are using a correct burning rate of powder by how close the velocity of the reload matches the velocity of the factory rounds. Note; You can easily, using PRE, match the pressure of factory 180 gr loads using Bulleye powder. However you will not match the velocity now will you. Using an appropriate powder you can duplicate factory pressures and velocities. Using some powders you may even be able to increase velocity while duplicating equivelent factory pressures. Without a chronograph you won't know this.

Hot Core says to leave the chronograph at home or trash it. Obviously he is thoroughly unaware of the value of using a chronograph as one tool in developing quality reloads that perform.

Larry Gibson

Hi Hot Core thanks for the link. Very informative and easy to follow.

quote:

One of our buddies uses "Groove Expansion"

This might be an interesting study as the groove is machined and should be round and the case usually isn't round making a reading a bit more difficult....interesting idea.

Thanks folks. I do have a problem in that there are no factory loads to match my own.
Just another question regarding PRE and CHE. I have suggested before that soft metals 'flow' under pressure and time. This means that a short duration, high pressure load could look the same as a lower pressure, longer duration load. This was speculation on my part initially but I have since had confirmation that this does indeed happen (but I cannot remember where I came across it).
Larry, you would be in a position to actually put this theory to the test. May I tempt you?

303Guy

It's already been done and is accepted as fact. CHE (when you get a valid measurement only measures peak pressure. That is the same with C.U.P. pressure measurement. The peak pressure that deforms the brass can be of short or long duration. Neither method can tell the difference as expansion will be the same for both.

I'll mention here that the main difference between CHE and C.U.P. is that with C.U.P. there is a tarage table that comes with the brass cylinders that tells how much pressure it took to crush it so much. With CHE there is no such tarage table for the cases used. You are only guessing/assuming that so much expansion equals so much peak pressure. That is, if you get a measureable amount of expansion. Hot core always whines about "reference ammuntion" to "calibrate" strain gauges (reference ammuntion is not used to calibrate any pressure device BTW) but fails to comprehend that there is no "reference case" to calibrate CHE. All the modern methods of measuring pressures, including reliable strain gauge methods, measure not only the peak pressure but also the time pressure curve. CHE and PRE do not do that. That's why chronographs, contrary to Hot Core's derogatory statements regarding them, are a valuable tool when reloading. A chronograph is of particular value if you are attempting PRE and CHE when developing loads.

Another thing of interest is how much pressure it takes to expand the case itself. If you have a chronagraph try this simple test. With the same lot of 15 cases (cartridge type is not relevent) Keep 5 that are not fired and fire the others with your standard load for that cartridge. Now load all 15 with that same standard load; the 5 unfired cases, neck size 5 and FL size 5. Then chronograph each 5 shot string. You will most often find the five neck sized cases to give the highest velocity, the five FL cases the next highest velocity and the new unfired cases to give the lowest velocity. Why? It takes pressure to expand the cases. The NS'd cases require the least, the FL sized case the next and the new cases the most. The pressure to expand the cases is actually energy. That energy used to expand the cases is therefore not used to push the bullets. Ergo the case that requires the most expansion has less energy pushing the bullet and there fore less velocity. It's most often a small amount (the most I've measured is 50 fps or so difference in '06 sized cases) but none the less measureable and interesting.

Larry Gibson

That's very interesting Larry, thank you.

doughnut eating radar-runners.

quote:

Originally posted by Larry Gibson:

I'll mention here that the main difference between CHE and C.U.P. is that with C.U.P. there is a tarage table that comes with the brass cylinders that tells how much pressure it took to crush it so much. With CHE there is no such tarage table for the cases used. You are only guessing/assuming that so much expansion equals so much peak pressure. That is, if you get a measureable amount of expansion. Hot core always whines about "reference ammuntion" to "calibrate" strain gauges (reference ammuntion is not used to calibrate any pressure device BTW) but fails to comprehend that there is no "reference case" to calibrate CHE. All the modern methods of measuring pressures, including reliable strain gauge methods, measure not only the peak pressure but also the time pressure curve. CHE and PRE do not do that. That's why chronographs, contrary to Hot Core's derogatory statements regarding them, are a valuable tool when reloading. A chronograph is of particular value if you are attempting PRE and CHE when developing loads.

oscarhans,

Larry is correct. The CHE method of determining pressure is long discredited. The only accurate way to measure pressure available to a reloader is the strain gauge method and most don't want to glue one of those to their hunting rifle. The problem with the CHE method, as Larry mentioned, is that there is no reference standard. Say you measure your cases and they expand XXX amount after firing. So what? It's meaningless. You have no idea what are the deformation properties of that particular lot of brass. Even if you did have some kind of scientifically determined data on that particular lot of brass it wouldn't mean much because brass is a poor medium for the range of pressures that a rifle operates. That's why the old laboratory method of pressure measurement used Copper crushers, not Brass crushers. Copper deforms predictably in the range of pressures that a rifle operates, brass does not.

All in all the CHE method is as accurate as reading tea leaves to determine pressure. At least with the tea leaves you get to drink the tea afterwards so it does have some benefit. CHE has none.

quote:

The problem with the CHE method, as Larry mentioned, is that there is no reference standard. Say you measure your cases and they expand XXX amount after firing. So what? It's meaningless. You have no idea what are the deformation properties of that particular lot of brass.

May I take exception with this comment please.....

Because the brass case is the "fuse" or weak point in the firing of the cartridge, it makes perfect sense to measure it's deformation.

Granted it can vary in hardness but that's precisely why we measure it.....

I 100% concurr that CHE does not indicate any kind of pressure reading.....say in CUP or PSI etc but it does tell me how that specific piece of brass is standing up to the pressure in the combustion chamber and that's all I care about.

If my brass is so poor that it starts to flow at 45,000 PSI, then I can see it as it's starting to fail....same if it's quite hard brass and doesn't start to fail until 80,000 PSI.

In other words....it's totally irrelevant what pressure I'm incurring....it's only relevant how the weak point....the brass case.... is standing up to the pressure.

If I'm using a modern bolt rifle that can stand extreme pressures then my only concern is the brass case....how's it standing up to the loads I'm using....and CHE does in fact give me an indication to that specific question.....in fact I really don't give a care in the world what the pressure is.....

Again....if you want to measure pressure then I fully agree that CHE don't tell you a thing....it's a worthless exercise.....but if you want to maximize the loads your particular brass can handle then CHE becomes a very valuable tool!.....I just happen to choose the latter.

Nicely expressed,VD. roger

quote:

Originally posted by bartsche:
Nicely expressed,VD. roger

Thank you Roger.....seems at times the mechanic can get so carried away explaining how his wrench was made that he forgets to install the spark plugs.

Vapodog

Here's the inherent problem with that. Many times pressures are way over the top before you get any case head expansion. Let me give you an example.

I recently conducted pressure tests of .223/5.56 ammuntion. I was using a 21" TC Contender with factory barrel. This barrel has a tight .223 chamber and a .224" barrel. Twist is actually 1-11". The pressures were measured with the Oehler M43. I also was taking case head measurements as I was going to fire 5.56 in the .223 Remington chamber...a considered "no-no" by many. MAP for the .223 is 55,000 psi and MAP (CIP) for the 5.56 is 60,000 psi. The test went as follows;

10 rounds of Remington 50 gr HPs (L223R8) and it had a MAP of 52,900 psi(M43) and a velocity of 3280 fps - right where it should have been. No case head expansion.

10 rounds of my favorite (max) .223 reload (55SX over 26.5 gr H335). It had a MAP of 58.200 psi(M43) and a velocity of 3183 fps. These cases had been fired many times so no attempt at case head measurement was taken.

10 rounds of LC00 M193. It had a MAP of 56,900 psi(M43) and a velocity of 3234 fps, well within specs. No case head expansion.

10 rounds of LC82 M193. It had a MAP of 60,500 psi(M43) with a velocity of 3271. Top end of specs. No case head expansion.

10 rounds of LC91 M193. It had a MAP of 56,200 psi(M43) with a velocity of 3230 fps, well within specs. No case head expansion.

10 rounds of Winchester M193 "white box" commercial ammo I purchased a few days before the test at Cabella's. Headstamp was WCC07. It had 27 gr of ball powder under the 55 gr M193 FMJ bullet. It had a MAP of 65,700 psi(M43) with the top peak pressure being 68,300 psi(M43). Velocity was 3351 fps. Case head expansion was .0003 - .0005".

Now then lets look at the following "rules" from Hot Core's CHE method;

"15. Continue the Testing until a 0.0005"- 0.0007" Case Head Expansion is attained or the “Factory Standard Pressure Value†is duplicated.
16. You have now created a SAFE MAX Load for this Lot of cases.
17. This Load can be SAFELY duplicated in Lots from the same manufacturer where the weight of those cases is the same or less.
18. This SAFE MAX Load is for this one specific firearm ONLY!"

If we look at the above test I ran we see that the Winchester 'white box" ammo was still not a "safe maximum" according to Hot Core's standards for CHE. Yet not on ly does the velocity give a warning that pressures are over the top but the actual pressures are indeed "over the top". Should the Winchester ammo have been loaded with those componants to a case head expansion of .0005-.0007" as Hot Core says is a "safe maximum load" then we would have been into proof load pressures.

A constant diet of proof loads deemed "safe maximum loads" by CHE is not a very good place to be now is it? That is a prime example of how CHE has been discredited and why it is unreliable. In your example with the case being the "fuse"; if your cases do flow at 45,000 psi you are indeed pretty safe. However, if your case do not flow until an unsafe pressure is reached then something besides the "fuse" could blow. The problem is you do not know at what psi your cases will flow, ergo your "fuse" is unreliable.

Larry Gibson

quote:

Larry Gibson

Please take your disagreements with Hot Core to Hot Core.....I'll stand by my post!

Mmmm.... Each stand-point presented here makes a lot of sense! Good to hear both sides of the debate.

I have the problem that I do not have a modern, strong rifle. Many of us don't. Hopefully, we understand that. It turns out that my particular rifle was also chambered in 222, so it would be safe for me to load my hornet to an equivalent bolt thrust - meaning 47,000 CUP will be safe in my rifle. But factory ammo is supposed to be loaded to no more than 43,000 CUP. I wouldn't dare to load until the primers pierce or the primer pockets loosen. I have gingerly edged up until I achieved consistent accuracy.

Another factor to consider is that the size of the case and the pressure time-curve will influence brass flow. This means that the 223 might 'under-read' using CHE.

The thread on 'exploding' Mausers shows that in that instance, the danger is not the pressure but the failure of the case.

quote:

I have the problem that I do not have a modern, strong rifle.

303Guy....may I heavily encourage you to invest in a Remington 700 rifle or other strong bolt rifle.....Savage makes an enormously strong action and is quite cheap.....it just may pay you back some day in the form of fingers, eyes, facial scars.....

FWIW I wouldn't reload for a rifle that didn't have among it's virtues the case as the weak link.

quote:

Originally posted by vapodog:

quote:

Larry Gibson

Please take your disagreements with Hot Core to Hot Core.....I'll stand by my post!

vapodog

The post was, while directed at you in response to your previous post, was directed at all those who may read such messages as yours and feel that CHE is safe. It is not. I presented facts that show where it fails. I did not expect you to change your opinion and certainly didn't expect any more of an answer than that from you.

I would discuss the issue with Hot Core should he demonstrate a reasonable attitude and a willingness for a factual discussion. However his last post above adequately demonstrates his rude and non-intelligent form of discussion of which I shall not engage.

Larry Gibson

quote:

Originally posted by boltman:
...The problem with the CHE method, as Larry mentioned, is that there is no reference standard.

Hey Boltman, That is because you simply do not understand what is going on when measuring CHE. And of course the doughnut-eating radar-runner(d-e r-r) really doesn't have a clue about the reality of Pressure nor Internal Ballistics.

It does surprise me that the d-e r-r is able to PT Barnum you.

quote:

Say you measure your cases and they expand XXX amount after firing. So what? It's meaningless.

This is also totally wrong. It has been proven over the years that CHE is the only acceptable Pressure Detection Method available to the normal Reloader(on High Pressure Cases). There is an Upper Limit to the CHE, because Primer Pocket Expansion becomes evident if a person does not understand when to STOP dumping in Powder.

quote:

You have no idea what are the deformation properties of that particular lot of brass.

Actually a person does if he measures CHE properly. Since the "Case" is the weak link in the normal Firing Process, how much the specific Lot of Cases Expands, is the critical issue.

quote:

Even if you did have some kind of scientifically determined data on that particular lot of brass it wouldn't mean much because brass is a poor medium for the range of pressures that a rifle operates.

I'm at a loss to understand how ANYONE the Reloads could possibly be that uneducated about the actual Firing Process.

ANYONE who believes Boltman's last statement is correct - should STOP Reloading immediately.

quote:

That's why the old laboratory method of pressure measurement used Copper crushers, not Brass crushers. Copper deforms predictably in the range of pressures that a rifle operates, brass does not.

I'm a bit surprised at the number of times we go over this subject on the Board and there are people whom I normally think of as rational and educated which still don't understand how and why the CHE and PRE Processes work. Amazing!

quote:

All in all the CHE method is as accurate as reading tea leaves to determine pressure. ...

This is one of the Stupidest Statements of ALL TIME. CHE and PRE have worked well for over 100 years and will continue to work long after we are all gone.

d-e r-r

quote:

Savage makes an enormously strong action and is quite cheap.....it just may pay you back some day in the form of fingers, eyes, facial scars.....

Well,..... maybe one day I will. It is of course, a very logical viewpoint.

Funny thing 'though, I have only ever heard of strong, Mauser type actions blowing up! (Or splitting the receiver ring and letting the barrel go down range). A gunsmith showed me a broken P-14 Enfield locking lug - supposedly a very strong bolt. I know the Lee Enfield can be made to fail but I have just never heard of it happening to a reloader. But actually, I do not see reading primers as a problem normally, it's just that I was expecting to see the same pressure signs on my cases as I see on the primers and that did not happen! This was with a new case. The old cases had long since expanded to the chamber dimensions. My test on the new case was to check that new cases with the same load would not go 'excess'. Now I am thinking that my loads are not as hot as I had previously thought. That's a good thing! (My hornet is a beautiful little rifle and I do not want to ruin it!)_

quote:

Originally posted by Hot Core:

quote:

Even if you did have some kind of scientifically determined data on that particular lot of brass it wouldn't mean much because brass is a poor medium for the range of pressures that a rifle operates.

I'm at a loss to understand how ANYONE the Reloads could possibly be that uneducated about the actual Firing Process.

ANYONE who believes Boltman's last statement is correct - should STOP Reloading immediately.

Here's the full text of what I actually posted:

quote:

The problem with the CHE method, as Larry mentioned, is that there is no reference standard. Say you measure your cases and they expand XXX amount after firing. So what? It's meaningless. You have no idea what are the deformation properties of that particular lot of brass. Even if you did have some kind of scientifically determined data on that particular lot of brass it wouldn't mean much because brass is a poor medium for the range of pressures that a rifle operates. That's why the old laboratory method of pressure measurement used Copper crushers, not Brass crushers. Copper deforms predictably in the range of pressures that a rifle operates, brass does not.

Obviously I'm referring to the ability of brass to deform predictably and to gleam reliable pressure data from that deformation over the range of pressures which a rifle operates. I am not saying that brass is not suitable as case material as Hot Core is hinting. Either Hot Core isn't capable of basic reading comprehension or he deliberately chopped it in order to present it out of context. In either case it's obvious what I meant when the statement is read in it's entirety.

quote:

Originally posted by Hot Core:

quote:

All in all the CHE method is as accurate as reading tea leaves to determine pressure. ...

This is one of the Stupidest Statements of ALL TIME. CHE and PRE have worked well for over 100 years and will continue to work long after we are all gone.

CHE and PRE haven't done shit over the last 100 years. The mere coincidence that people haven't been blowing up their rifles while using a scientifically invalid method like CHE doesn't establish it's validity, it just means that most rifles are built to be idiot proof. Primitive peoples have been dancing for rain for 200,000 years and every now and then it rains. It doesn't mean that the dance caused it. The guy that first came up with the CHE method, Ken Waters, admitted later that it was bullshit when better instrumentation became available and it was obvious the method was based upon false assumptions. At least he had the decency to admit his mistake. If only we could get the same thing out of some of our more hardheaded forum members then maybe this crap would all go away and we could finally stop spreading false information.

The good thing is that if you rely on CHE and a reloading manual you probably won't blow up your rifle or yourself due to the safety margin built into modern firearms. The bad thing is that you still won't know a damned thing about how much pressure you've got.

quote:

Originally posted by boltman:
...The guy that first came up with the CHE method, Ken Waters, admitted later that it was bullshit when better instrumentation became available and it was obvious the method was based upon false assumptions. At least he had the decency to admit his mistake.

Can't imagine who or where this "WRONG" idea came from, because CHE & PRE were both in use prior to the Reloading Genius Ken Waters ever being born. I've never seen Mr. Waters say anything bad or negative about either Method. He has always championed both methods as has Bob Hagel.

quote:

If only we could get the same thing out of some of our more hardheaded forum members then maybe this crap would all go away and we could finally stop spreading false information.

Completely agree.

quote:

The good thing is that if you rely on CHE and a reloading manual you probably won't blow up your rifle or yourself due to the safety margin built into modern firearms. The bad thing is that you still won't know a damned thing about how much pressure you've got.

And Wrong again.

No desire to argue with Boltman, however it is important to not let his ignorant statements stand without challenge. I do agree with Boltman on a lot of stuff, but concerning CHE & PRE, he has a lot to learn.

And no need to argue with the d-e r-r since no one with any sense believes anything he posts anyhow. Wake up 303Guy!

d-e r-r

A little side light for those interested.

The Hodgdon reloading manual #26 printed 1993 was originally one of my favorite manuals (along with the Hornady manual)

It shows a max load for a 180 grain bullet for the .308 winchester as follows:
IMR-4064....42.0 grains....2488 FPS at 51,200 CUP

Years ago I worked up the following load in my 700 Remington
IMR-4064, 45.5 grains ....180 grain bullet.....2740 FPS.....and .0003 growth CHE

Today if you go to Hodgdon's website we see the following data:
.308 Win 180 grain bullets, IMR-4064 45.2 grains, 2683 fps, 58,200 PSI

This brings up a few interesting questions..... like how accurate was the old CUP readings?....like how consistent are the powder specs manufactured to? (BTW....the IMR-4064 powder I'm using was purchased before 1993)

Incidently, this is a fairly compressed load and I'm fairly certain another grain can be added if one chooses but I stopped with the readings in CHE

For those that want to "lamblast" CHE as worthless, your words are falling on deaf ears here..... It has never been my only pressure sign and never will be....it's one of the usual many and today I use primer pocket expansion more than CHE but still break out the Mitutoyo blade micrometer when I'm looking for a serious load.....

For those using new strain gage technology to measure pressures, I cheer you on.....I know absolutely nothing about them and frankly have very little interest.....If the "big companies" using CUP measuring tools were so poor as to publish the above results it does make one ponder the accuracy of less costly tools...I take no sides in the strain gage discussions again as I know nothing at all about their use or limitations....Have at it guys.....I'm keeping my old mitutoyo blade mike!

Boltman

You've probably noticed by now that it is impossible to reason with Hot Core. He made his stand with CHE sometime back and is sticking to it. That's ok as i'll continue to post so new members will not be led down that path. Hot Core also attempts to insult me as I was a LEO for some years. I am rather proud of that service and he stupidly continues with the radar bit. I seldom used radar as it was not generally available when I worked traffic. I did and still do eat donuts though (yum, yum!). That was a habit I picked up from my grandmother who made them. I've also noticed over the years that most who use such derogatory terms as Hot Core does are the very ones who have numerous contacts with LEO under advasorial conditions. His comments speak of and reflect on his charactor.

Larry Gibson

quote:

Wake up 303Guy!

I'm not taking sides here.
I'm not disregarding anybody's viewpoint. I am looking for the positive value of both sides of the debate. I think the truth lies nearer the middle. Anyway, listening to all sides allows me to keep an open mind and gives me something to think about. Besides, I have no other means than CHE and PRE and primer flattening to gauge pressure levels. And perhaps a dose of common sense! The problem with CHE as I see it is that the changes we are looking for are very small and take very careful measuring. The differences in reading at various points around the perimeter of the head are greater than the expansion itself so one has to be very careful to measure in exactly the same place each time. (And take several readings at different points). And then it doesn't work for me due to the low pressures I have to keep to.

With regard to the 'unpredictable' nature of brass cases, just how much does the strength of cases vary from batch to batch and brand to brand? What would happen if we were to anneal the cases before commencing load work up? Of course we would only be able to use each case just once but wouldn't this give us an idea of the correlation between pressure increase and powder charge increase? (I know that the cases will not fail completely because I accidentally annealed some brass and it only bulged. That was in a mini-14 with no case head support in the chamber at all. Well, I only fired the one then disassemble the rest!)

303guy

It is nice that you want to be polically correct and "think the truth lies nearer the middle". However your whole last paragraph tells us that you do not think such. Your last paragraph is essentially correct BTW. There is too much variance in cartridge cases for CHE to be reliable.

Since you only have the resourses that most all reloaders have for your lower pressured cartridges then you must stay within load recommendations and use a chronograph. PRE is also useful if you have factory ammuntion. However use the unfired factory cases to develop your loads in as I previously mentioned. Using those unfired cases makes matching factory pressures pretty reliable. However, a reminder that PRE also only measures the peak pressure so use a chronograp also. The chronograph will not tell you pressures but it will tell you when you are where you want to be with appropriate componants similar to factory componants.

If your velocity equals the factory velocity with equal PRE measurements then you have duplicated the factory load essentially.

If your velocity is less than factory velocity with equal PRE measurements then your load has a faster time/pressure curve than the factory load.

Conversely if your velocity is faster than factory velocity with the same PRE mesurement then your loads time/pressure curve is slower than the factory ammuntion.

If you have equal or faster velocity than the factory velocity with a smaller PRE measurement than factory PRE measurements then you have a load with less pressure and a good slower time/pressure curve.

I agree with Hot Core on the validity of PRE (when done with unfired factory cases as I've mentioned). It is the validity of CHE that Hot Core and I disagree on. I measure pressure and know that CHE is not reliable, he does not.

Hot Core; coffee and doughnuts sometime?

Larry Gibson

quote:

...I've also noticed over the years that most who use such derogatory terms as Hot Core does are the very ones who have numerous contacts with LEO under advasorial conditions.

Nope, wrong as usual. Haven't even had a speeding ticket since `71.

People get this attitude from watching the doughnut-eaters running-radar while Drugs are being sold next to them on the streets. A total waste of resources and TAX money.

Or when it is impossible for the old folks to get help when needed because they are way too busy parked behind a building sleeping on duty.

Then when they get there and dust the doughnut crumbs off, they want to arrest the old folks because they eliminated the problem - pitiful!

quote:

...Hot Core; coffee and doughnuts sometime?

HEY!!! No need for the nice guy routine. I have enough trouble coming across as being mad at you CHE/PRE Bashers as it is - because I'm so Inherently Amiable!
-----

quote:

From NZ via 303Guy:
I'm not taking sides here.

I'd guess you will eventually find a few "Barbs" located along that fence you are straddling.

quote:

I have no other means than CHE and PRE and primer flattening to gauge pressure levels. And perhaps a dose of common sense!

OK, I'll admit that is what generally keeps people from being able to understand and properly use the always-reliable, never-fail, venerable and versital - CHE & PRE - just a lack of Common Sense.

quote:

The problem with CHE as I see it is that the changes we are looking for are very small and take very careful measuring. The differences in reading at various points around the perimeter of the head are greater than the expansion itself so one has to be very careful to measure in exactly the same place each time. (And take several readings at different points).

I'd recommend you stick with "1-point" on each Casehead, but load a few at each level and Average the results, when working with Higher Pressure cartridges than the ole 22Hornet. You are correct that taking accurate measurements is very important, something impossible to do with a non-calibrated, guessed at chamber dimensions, and fudge factored HSGS.

quote:

And then it(EDIT IN: CHE) doesn't work for me due to the low pressures I have to keep to.

Absolutely correcto! Fortunately the good old always-reliable, never-fail, venerable and versital PRE will work perfectly for you, as it has for well over 100 years.

You can also use Pistol Primers in the old 22Hornet as a very reliable Upper Pressure Limit Indicator - "IF" - your specific rifle and Shooting Glasses are capable of protecting you from a Pierced Primer. As a nice side benefit, the Accuracy is often enhanced by using Pistol Primers.

quote:

Nope, wrong as usual. Haven't even had a speeding ticket since `71.

People get this attitude from watching the doughnut-eaters running-radar while Drugs are being sold next to them on the streets. A total waste of resources and TAX money.

Or when it is impossible for the old folks to get help when needed because they are way too busy parked behind a building sleeping on duty.

Then when they get there and dust the doughnut crumbs off, they want to arrest the old folks because they eliminated the problem - pitiful!

Well, looks like your'e wrong as usual too!

I never slept on duty and didn't need to park behind any building unless on a stake out. I spent most of my time on criminal investigations and arresting the drug sellers. Got in trouble for doing too good a job. The money from that crap runs pretty deep. I helped anyone, regardless of age, who needed it. I also never arrested anyone who hadn't committed a crime. I won't disagree that there are many problems with many police officers. I've seen too many of them myself. I tried to do something about it once and lost. I'm rather proud of my police service. I really wouldn't mind having coffee and donuts with you BTW.

Larry Gibson

Also chamber dimensions aren't any harder to measure than case heads. Don't need to "guess" about either.

quote:

I'd guess you will eventually find a few "Barbs" located along that fence you are straddling.

I hope not! You folks really do have valuable viewpoints, the both of you! I always enjoy 'listening' to you folks! FWIW, I think you two folks both make a huge contribution to this forum!

Thanks for the heads up on the pistol primers Hot Core. It is what I have been doing for years (but was always too embarrassed to talk about it!)
I have never gone anywhere near piercing a pistol primer. I only looked at primer edge and indent edge flattening and cratering. My hornet craters all the time but then again it makes a small dent to start off with. Could this be a problem - insufficient firing pin force?

So, .... what do you folks think of the annealed brass idea? (I am thinking of the lower end or starting load range). I am not confident or bold enough to just jump in and try it!

P.S. I have mentioned before that I accidentally (well, negligently) loaded up a WW case and had an over-flattened primer and loose primer pocket. The cratering around the firing pin indent was normal. (No sign of imminent primer piercing).

My take is that the 1889 7.63x53mm Mauser .470" base case head design used in the 30-06 and other cartridges has a weak spot around the primer pocket.

The number of firing a load can get before the primer pocket is too loose to re use is a good measure of a load.

I have reloaded the same case over and over at the range to test case life.
That is a real pain.
The pain is not the reloading at the range.
The pain is getting the reloading equipment boxed up, transported, set up, boxed up, transported, and redistributed at home.

A much better system is to do a work up in one grain increments and measure the extractor groove expansion with dial calipers. This indirectly measures the primer pocket expansion.

When the primer pocket expands [the plastic part of the deformation] it can be measured with pin gauges, but that has problems. The pockets are dirty and the tolerances are tiny.



Now with 303 Brit brass fired in a No.4 mk II, the case life expansion problem is longitudinal case head separation, not radial primer pocket expansion, like in a Mauser case head.

One fact is certain; When the case head expands
the brass has reached its yield stress. With that brass.
with that load, in that chamber it is time to
start thinking about what you are doing.
Good luck!

quote:

Originally posted by 303Guy:
...With regard to the 'unpredictable' nature of brass cases, just how much does the strength of cases vary from batch to batch and brand to brand?

Good question which can only be answered by measuring CHE, PRE and Groove Expansion(Primer Pocket Expansion). Until Dr. Oehler gets off his duff and comes out with the Hot Core Model(minus all the HSGS fiasco, but with the ability to measure both CHE & PRE) there is no way to know how the Case is responding to the increasing Pressure other than CHE, PRE, and GE. You sure don't know by measuring Velocity or with a HSGS fiasco.

quote:

What would happen if we were to anneal the cases before commencing load work up?

It depends on how many times the Case has been fired and the Pressure levels it was subjected to. If done properly, PRE will provide excellent, usable, data for 5-6 Reloads, depending on how HOT the Load is.

quote:

Of course we would only be able to use each case just once but wouldn't this give us an idea of the correlation between pressure increase and powder charge increase? (I know that the cases will not fail completely because I accidentally annealed some brass and it only bulged. That was in a mini-14 with no case head support in the chamber at all. Well, I only fired the one then disassemble the rest!)

You have lost me in this paragraph because all Cases "Bulge" when subjected to Pressure, that is how PRE works.

here is a good article
http://www.shootingsoftware.com/ftp/dbramwell%20july%2019%2004.pdf