Load Development To Determine A Rifle’s Actual “max” Load.

[Wildfire]

Ol' Joe.

Hey :
Very interesting reading, Thanks. I was very aware of primer pockets expanding and have seen much of that type of thing happen to IPSC shooters with their hand guns. trying to make major with lighter bullets.
Or using brass that should not have been used. Saw some of the same thing happen to guys that pick up range brass for rifles too. They have no idea what they are getting or how many times it was fired. If someone left it there , they were done with it. Never made sence to me to take seconds.

 

[.38 Special]

Pressure estimation through case head measurement.

Of particular note: "Better yet, we can observe a working maximum charge BEFORE any other signs of over-pressure even begin to appear. It is this ability to observe the APPROACH to maximum pressure that is so valuable. All other methods of judging pressure reveal only that a safe maximum has been PASSED. " (Bolding is mine, as it perfectly states my argument against the OP's method.)

<edit> FWIW, the author of the above article strongly recommends the reader familiarize himself with the work of Ken Waters, and I strongly second that opinion.

 

[Wildfire]

Wow.

Hey there again.
After looking at the two different sites, OL'Joes and 38s. well according to the one OL'Joe has provided us "any change in the case head size is too much"
The 'Rockys " site starts to give us size limits. Which one is correct????
The One that OL'Joe has given us seems to be very informative and is likely the one I would have to study up on.

Thanks for both.

 

[Bullet]

This probably says it all - From Ol` Joe’s link -

Case Head Expansion, or CHE, is a measure of how much the solid brass case head
expands when the cartridge is fired. The measurement is normally taken just in front of
the extractor groove. Pressure Ring Expansion, or PRE, is simply a measure of the
diameter of the pressure ring that occurs just forward of the solid brass portion of the
cartridge, and is not a difference.

Conclusions
1. CHE and PRE do provide some information, but it’s mixed with a lot of random noise.
The mix contains more random noise than information.
2. Both the PRE and the CHE methods do poorly at giving the same answer when
comparing cases subjected to near-identical conditions.
3. A measurement system can be useful, even if it is imprecise. The problem is that
PRE, the better of the two systems, can just barely distinguish a plinker load from a barrel
buster. That’s only two categories, and not very useful. You can average to improve
precision, but it takes an impractical number of cartridges to get a questionable standard
of comparison.
4. PRE and CHE always do always give an answer, but I can give you a random number
table that is almost as good. That has the added advantage of not requiring a micrometer.
Since firearms are typically very conservatively designed, your chances of blowing one
up are slim, as long as you stick to reasonable powder choices. The illusion is that the
methods work. The fact is that both methods can lead you to think that you are safe,
when, in fact, you are punishing your firearm.
5. In preparing this article, I spent $200 on a flat granite plate, and the nicest used
electronic blade micrometer I could find. I have other uses for these tools, which is a
good thing, because their cost exceeds that of a strain gage system, and they are a poor
indicator of whether my cartridges are safe.
6. Since conventional pressure signs did not develop, even at 10,000 PSI over limit, it
seems that they are not a reliable indicator, either. That seems to narrow the field of safe
options to three: 1) Use commercial ammunition. 2) Reload, and stick to the book
loads. 3) Reload, study the books, and get a strain gage.
7. As the title of the article suggests, both the PRE and CHE methods should be retired,
and “Rest In Peace”.

6. Since conventional pressure signs did not develop, even at 10,000 PSI over limit, it
seems that they are not a reliable indicator, either. That seems to narrow the field of safe
options to three: 1) Use commercial ammunition. 2) Reload, and stick to the book
loads. 3) Reload, study the books, and get a strain gage.


.

 

[Wildfire]

Good ol #7.

Hey there.
Didn't catch #7 the first time thru. Kind of settels the whloe issue for me. Thanks Bullet.

 

[Bullet]

I’m no expert and I don’t have a strain gage so I’ll just stay with my manuals. If my bullet isn’t going fast enough I’ll go to another cartridge where the bullet speed I’m wanting is listed in the manual. Seems like if you do this you won’t get in trouble.

 

[Wildfire]

I agree.

Hey there:
I could not agree more. None of my loads even come close to max loads.
I want MAX accuracy not velocity.

 

[Bullet]

In my 308 the most accurate load I’ve found isn’t a Max velocity load.

 

[steve4102]

It is not surprising to me that the author(Denton Bramwell) of O'Joe's link suggests the use of a "Strain Gauge", and that PRE and CHE are worthless. After all he is the inventor of the RSI Strain Gauge. Would only make sense to push his own product.

 

[USSR]

It is not surprising to me that the author(Denton Bramwell) of O'Joe's link suggests the use of a "Strain Gauge", and that PRE and CHE are worthless. After all he is the inventor of the RSI Strain Gauge. Would only make sense to push his own product.

Thanks for pointing that out Steve. As I have previously indicated, THERE IS NO ONE INDICATOR OF A MAX LOAD FOR EVERY RIFLE (and that includes the reloading manuals). Load development is best approached using the many indicators I have mentioned in conjunction with one another, so as to remain within a safe pressure range for your cartridge/platform.

Don

 

[sublimaze41]

A few years ago I wanted a round that would go over 4,000 FPS. I was sure I could get it in a .22-250 with a 40 grain bullet, but wanted to shoot at least a 55 grainer. Couldn't afford A Swift.

I went through a whole bunch of data and finally worked up a load for my .243 that shot a 55 grainer over 4,000 FPS. It was published data and the chronograph verified it as true. No pressure signs were observed. The accuracy was so-so.

Later I proudly posted my results here or a like board. Someone chimed in something like this, "why do you want to have the velocity over 4,000 FPS?"
Someone else ask if this was my most accurate load, it was not. My most accurate load was a 58 grainer with 4350 at a much slower speed. Someone else ask why I wanted to lower the safety margin to a razor thin point.

I still have 20 of those rounds that took so much effort to load. I still can't bring myself to shoot those rounds. Why would I want to shoot them when my 58 grain load is dead solid at 500-600 FPS less and produces no anxiety with a pull of the trigger.

 

[Ol` Joe]

It is not surprising to me that the author(Denton Bramwell) of O'Joe's link suggests the use of a "Strain Gauge", and that PRE and CHE are worthless. After all he is the inventor of the RSI Strain Gauge. Would only make sense to push his own product.

Steve Denton isn`t the inventor of the Pressure Trace or a employee of the company that I`m aware of. He is a Gun writer for "Varmite Hunter Magazine". The articals on the RSI site are from published articals he wrote for the magazine and reprinted with permision.

Denton Bramwell is a regular contributor to Varmint Hunter Magazine. His continuing series of articles in Varmint Hunter about load pressure issues are some of the best we have seen. Mr. Bramwell is a physicist and statistician with a background in measurement instrumentation. His conclusions are always supported with good data and proper analysis. When not shooting to gather data for another Varmint Hunter article, Denton is consulting with design engineers. To learn more visit his company's web site at: www.pmg.cc.

The following copyrighted articles articles were provided with the permission of Varmint Hunter Magazine and Denton Bramwell for your personal use only.

There are a number of firearm writers that don`t rust the "case head/ pressure ring expansion" method of deeming cartridge pressure. Ken Howell, John Barsness, Rocky Raab and a few others have commented on its weak points on a couple of forums. These two links have a bit more to offer on the subject from a couple of them.

http://www.24hourcampfire.com/ubbth...quot;)+pressure&topic=0&Search=true#Post60136

http://www.24hourcampfire.com/ubbth...quot;)+pressure&topic=0&Search=true#Post53878

 

[steve4102]

There are a number of firearm writers that don`t rust the "case head/ pressure ring expansion" method of deeming cartridge pressure.

I do not trust this method for deeming cartridge pressure either. I have given up on this technique a long time ago.

If Denton is not the Strain Gauge, can you tell me how he is affiliated with it? Every where I turn the RSI Strain Gauge and Denton come up on the same page.

 

[Ol` Joe]

If Denton is not the Strain Gauge, can you tell me how he is affiliated with it? Every where I turn the RSI Strain Gauge and Denton come up on the same page

I`m not sure how Denton fits in. I am guessing he conversed with the maker for some of his articals he wrote where he used the Pressure Trace. He wrote more then a couple for Varmite Hunter, and has personally recommended it on the web often.
You might give a call to RSI (Pressure Trace) and ask. The owner has always been very helpful to me when I`ve had questions and will talk for hours if you let him.
(928) 634-8028

 

[Wildfire]

Good deal.

Hey there:
I too think this is not good way to adjust loads. For one thing almost all of the "Pro's" agree that the primer hole wil get larger before the case head expands. That in and of itself dictates over PSI. If that is true , Then the expansion of the case head is Too late. IMO.

Leaks at the primer, Flatend primers, Rings at the right places on the case's and so on seem to me to be better warning signs. Exceeding max velocities would also be a rather simple indicator that we may be getting too hot.
Best I can tell the measuring of the case head has been done away with and was considered to be an unreliable source of loading information.

While it may not hurt anything to know that measurement, it appears as though it is not a safe way of determining PSI.

you all may have fun with this , I will be moving on. Thank you....

 

[243winxb]

Bumping to front. Pressure sign photos found here. http://www.photobucket.com/joe1944usa