We have been having a interesting and sometimes heated, and unfortunately not always civil as it could be discussion about determining pressure of handloads (See Chronograph vs Reload Manuals etc).

Hot Core is one of several who use the CHE/PRE method of "determining" over-pressure indications. I (and others) believe that this method (I'll treat them for the purposes of our discussion as one method) of determining over-pressure situations in handloads has been proven to be inaccurate, and I believe that its use is dangerous because it can lead a handloader to believe his/her loads are within safe limits when they are in fact over the safe limits.

For those of you who are interested please Google Oehler Model 43 and www.frfrogpad.com . While there is an article out there stating that the military needs high quality gages for testing cannons and they had one instance of gage "failure" which they could not explain, it is very clear that this is the method of choice for manufacturers and defense applications.

Because this is goes to the heart of our "sport," I would like to know what AR reloaders use/do to insure they are within safe limits (particularly those of you who reload wildcats and 'odd ball' cartridges.)

And Hot Core, this isn't really about you or your position. Kudude

I use PRE and find it to be a fairly reliable indicator of safe pressures -when narrowly confined in scope. Can PRE keep you safe? Certainly. Can it measure pressure? Certainly not. Applied randomly it indicates nothing, but when used with like components of the same lot and combined with chronograph readings I find that similar measurements, more often than not, generate similar velocities. Combine this information with other indicators such as the required force needed to open the bolt and primer condition, one can gain a very good idea of whether or not the loads in question are safe. Of course all of this assumes one can not only read a micrometer, but take repeatable measurements in the .0001" range.

CHE on the other hand is a meaningless exercise in frustration as far as I'm concerned. Given that the case head is solid and serves to hold the primer in place among other things, any and all expansion should be viewed as excessive.

I smell someone with a monopoly on the truth.

I exceed neither max loads nor max velocities. I look at primers, comparing them to factory loads.

I know primers don't tell all, but they tell enough. I know many will pooh-pooh the primer method, but it has kept me out of trouble.

in low pressure stuff like the 45-70, I use powders that keep pressures low, like 3031.

and when I need more speed, I buy a bigger gun.

it is very easy to keep out of trouble if you want to. it's less easy if you don't want to.

quote:

Originally posted by kudude:
...And Hot Core, this isn't really about you or your position. Kudude

Hey Kudude, I understand. You desire no opposing views(aka the truth).

I'd be reallllly interested in hearing about the great accuracy of the HSGSs.

Best of luck to you.

I don't have a chrono.
I had a 375 Whelen made some 20 years ago.
Loading data was scarce.
I used the loading data, using the same bullet weight, that is published for 35 Whelen.
Once I approached the top end I looked at the primers, since I had nothing else to work with.
I was working with cast bullets using jacketed bullet data, everything worked fine andstill does.

Jim

Hot Core,

I would really appreciate your cites to articles by gun scribes or technical articles supporting the accuracy of CHE or PRE.

I'll suggest to those who want to know the "truth" as we understand it that they Google strain gages + chamber pressures. Read what has been written by Oehler, RSI, and over at Chuck Hawks' page.

I think that the Chuck Hawks article summarizes the issue really well.

Kudude

/

Personally,
I measure the extractor groove diameter.
With an increase in powder work up, it has a distinct and repeatable threshold. A dial caliper is plenty sensitive to find this threshold in 2% powder increments.


Primers may fall out capriciously, but the cause of primer fall out, brass growth, is predicable.

I wish there were a good way to work that part of the brass, the sizing die does not touch it.

I don't believe either PRE, CHE, or anything else available to handloaders in my economic class will reliably tell handloaders exact pressures. But I also believe both can be useful tools when viewed as warning flags.

If primer pockets expand too much for one's comfort, then it probably doesn't matter whether the cause is high pressure, soft brass, or something else. It is time to reduce the load to a level at which the handloader DOES feel comfortable.

Ditto with greater than comfort-level case head expansion.

I use PRE and CHE as warning flags, and when coupled with chronograph readings (which also are not 100% precise pressure readings but ARE sometimes good indicators of when something is falling off the rails) they have served me well.

Sure, I may have been able to load hotter if I had a more reliable warning system available to me within my price range. But so what? If I had ignored the warnings PRE or CHE gave me, and then injured myself or my rifle, I would have to consider myself a greater fool than if I just didn't get the top loads I could have MAYBE gotten.

What is wrong with heeding ANY warning signs a person gets?

Why do we reloaders even want to know the relative pressures developed by our loads?

The answer may differ from one person to another. For most, though, I suspect the bottom line is "To keep from blowing themself up (or their gun)".

The handloader's brass is the weakest link for him in shooting's explosive chain. it is usually the brass which fails first if pressures are too high.

So how do we know if our brass is being maltreated? We look at it to see if it is being deformed, torn, holed, lengthened, shortened, or otherwise visibly altered.

Generally, we probably believe that if our brass is showing signs of unusual (to us) deformation, continued use of that load may become dangerous.

We may drop the load somewhat at that point, or we may risk leving it the same, if the deformation is not obviously severe. Surely, though, we seldom decide to see if we can resolve the problem by adding MORE pressure.

In other words, we see the changes as a warning, which if we are the average Joe, we heed.

So what are PRE and CHE, and where do they come in? Both are just a more organized method of determining the degree, if any, of brass distortion due to firing pressures.

Do they tell us what the firing pressures are? No.

Do they tell us if our brass is at fault instead of the powder charge? No.

They also tell us nothing about the condition of our rifle, the diameter or hardness of our bullets, or anything else.

Do they tell us when to continue using that load or to drop it, or to increase it? No.

Only our own brain(s) and ability to think can evaluate and make those decisions.

But are PRE and CHE useful at all then? Damned right they are. They bring to our attention degrees of brass change which we might otherwise not have noted.

If we don't know about brass changes, we can't decide what to do about those changes, or if we want to do anything. PRE & CHE, through the discipline of making measurements and recording them, force us to notice changes.

But only we can interpret and apply the warnings which PRE or CHE can give us.

An old saying warns us not to throw the baby out with the wash water. Perhaps that also applies to PRE and CHE.

Just because we choose not to use them hardly seems to justify thowing them away for everybody.