Pressure signs in the primers and excess bulging of the brass in the unsupported region of the chamber are two of the most common and easily recognized pressure signs that we handloaders have at our disposal to check for pressure issues. As you note, reading pressure signs in primers is far from exact, but is still a useful method.

Even excess bulging of the case has limitations, too, especially if your barrel offers full case support, in which case it might be useless.

Measuring the case head before and after to check for expansion is another method, but few of us bother to do this.

 

Pressure signs in the primers and excess bulging of the brass in the unsupported region of the chamber are two of the most common and easily recognized pressure signs that we handloaders have at our disposal to check for pressure issues. As you note, reading pressure signs in primers is far from exact, but is still a useful method.

Even excess bulging of the case has limitations, too, especially if your barrel offers full case support, in which case it might be useless.

Measuring the case head before and after to check for expansion is another method, but few of us bother to do this.

Good advice, particularly the last sentence. Even without exceeding safe load data for magnum revolvers, primers are going to be flattened more often than not. The abnormal conditions of primers such as cratering are more indicative. And remember that the correct case-head location varies by cartridge with an example being the 9 X 19mm where the location to check case-head expansion is .200" above the rim. Using a micrometer that measures in ten-thousandths will better allow you to observe the amount of case-head expansion even below standard pressure limits, but in the case of the 9mm and it's tapered case the bottom of the micrometers probes should be at .200" above the rim. It can also be done with a micrometer, but to no greater accuracy than reading between thousandths of an inch which are only approximations between thousandths.

I once read some articles by an astute experimenter of the .357 SIG and the 9 X 19mm where with the 9 X 19mm he advised that you may be getting close to an over-pressure condidtion when case-head expansion exceeds .001" over its pre-fired diameter. I load a lot of 9mm +P and I use a very limited number of powders to do so. In all cases thay have been proven pressure stable enough even for 9mm MAJOR loads that exceed the +P+ recommendation of 40,000 PSI. I just don't see any abnormal primer conditions that would make me believe my loads are over-pressure but I also take case-head measurements before and after firing.

 

I use data and ejection; is my load near, at, or over published data?

The other data is from my chronograph; are my bullets exceeding published velocities?

I observe ejection; do they launch to the moon?


I also might measure case head expansion with an accurate ten-thou mike; does my load make the case head expand more than control ammo case heads?
(Yes I have control ammo).

 

Case head measurement sounds like an interesting concept and makes sense. Anyone know of the threshold for 40sw in a ramped (supported) barrel?

I don't follow ejection since the 1911 I shoot in single stack is sprung so light (worn in 12lb with 180gr @ 945ish) that it will throw brass 15+ ft.

 

I have been loading Major Nine since 1995; there are certain things you get to learn (if you can learn) along the way.
One thing is powder choice. It's a big thing.


(Recent count showed 25 different handgun powders on my shelves).

 

Ejection does not tell you anything about pressure. It tells you about recoil.

But recoil can be significantly influenced by the gunpowder. In fact, one can get more recoil but lower pressure for the same velocity just by changing gunpowders.

 

not that I ain't afraid to blast past

I've always used this simple guideline for case head stuff; does MY load's measurements exceed those taken from my control load?

"Control load" example: 9x19 control load might be the case manufacturer's brand of high-performance +P/+P+ load(s).
Same thing in 40 S&W or others.

(I recommend high-performance BuffaloBore, CorBon, Garrett, DoubleTap, and the more common high-performance choices from: Winchester, Remington, Speer, Hornady, Federal).


Truth is it's rare to need to push hard enough to measure expansion, as I usually use chrono-mapping to determine what I consider MAXIMUM.
Then I measure to scare myself :dope:

 

I (on purpose) have matching pairs of guns.
In case I blow one up.

 

Clark, Clark, Clark! Is that you, Clark??!!!!

 

There are NO useful high pressure signs in semi-auto handguns. That is in the sense that there are no warning signs of approaching and exceeding SAAMI specs.

FREX I can shoot a pressure series in a .45 from Wadgun loads ( softball that won't disturb Bowmar heavy ribs) to GI Ball up to pressure limits for the .45 ACP then .45 ACP+P then .45 Super then .460 Rowland and folks won't beat guessing for ordering the pressure series. Much the same in a 9mm bore going from a 9x19 load to a 9x19 +P all the way up to 9x23 and again ordering a pressure series doesn't much work. Kidding on the square shooting a Bowmar rib loose or a Gold Cup sight loose may be a warning of something.

I haven't tried it but I suspect a series from .32 S&W Long to .32 H&R to .327 Magnum would give the same inconsistent results.

Blowing the magazine out the base and splintering the grips is of course a sign of over pressure. A kaboom is a sign of overpressure.

Otherwise figure the book load AT the book speed (accounting for barrel length and other such) is a useful sign of pressure - extra speed is extra pressure.

Despite popular belief to the contrary there are no really reliable pressure signs on the cartridge case for normal rifle loads either. One standard example is that when the 7mm STW was new a number of very savvy - or at least widely known - gun writers developed loads using pressure signs on the case and primer - these loads later tested over pressure in pressure barrels. The current book loads have been reduced from the early magazine articles.

Folks can get some information from things like a plunger ejector leaving an imprint on the case head and other signs of way over pressure loads in the circumstances but there is no useful sign to distinguish between say 30-40 pressures, .30-'06 pressures and .270 pressures - try to pick .270 SAAMI pressures from .280 SAAMI pressures and if you succeed tell me how.

Again in bottle neck rifle case a book load that matches book speed - adjusted for barrel length and atmospherics - is likely at the book pressures - faster is likely over book pressure.

Speer and Hornady and Waters and Bob Hagel have all written of using pressure signs to develop loads - I have a nice gage for measuring case head expansion to the nearest tenth - meaning to half a tenth or better and use the last digit as a guard digit - I bought from one of the big name bullet makers as used in their own lab for load development long ago. Savvy folks have abandoned that system because it doesn't work.

And finally notice that a gun used with enough over pressure loads will eventually fail with a SAAMI pressure load.

 

I like this dialogue. I can't add much, but two thoughts come to mind as I read the thread...


In the 1950's Richard Speer reported case head expansion .00003" (yes, 4 zeroes) to
.0005 (3 zeros) per shot at normal pressures. Wow, that's quite a spread. Jeepers!
He warned that it depends upon the particular brass you use and of course
the cartridge type. He further reported that excessive pressure can
expand case head 10 times that per shot. Sometimes. Again, it depends...
because different cartridges run at different pressure, and cases are designed
differently by different manufacturers, so there is no single 'right' answer.
That research is over 60 years old, but I gives you an idea of what you
might consider if you choose case head expansion as a metric.



Control ammo:
Doesn't SAAMI list standard control ammo for comparison in its test standards?
Gee, that would be great!!! Standard industry control ammo against which
you test your own reloads. That would be great !!! Go look it up to see if
it might be useful, or just Nick A not remembering very well.

 

Nick's answer to OP question:


Keep your eyes open for corrections or errata in the published manufacturer's data. Then trust the data.



Max load at manufacturer's data is determined using SAAMI standard methodology,
which includes modeling population criteria so that 97.5% of your handloads
are sure to be at or below max pressure. The other 2.5% overpressure events
(NOT on purpose, but true random variation) are within the capacity of a
modern gun in good serviceable condition. That's what SAAMI industry standards
are all about.

 

Way back I read that a dark ring around the primer is a sign of overpressure.
Might have been from Speers.

 

Speer's #10
page 79.
Dark ring around primer caused by primer leak.
They referenced the pics to excessive pressure.

I saw this in some test loads of 380 with twice fired cases and 115gr FMJ's. Win brass fired factory and then min-mid loads with the 115s
Primers went in and felt fine. CCI's
Ring was not very dark but caught my eye.
These were at the max loads with N320...Unique and Bullseye in my new Walther PPKS'.
Did not see this in the Sig238, LCP or DB380.
Have new Starline cases and will repeat my load work with the five pistols.

 

Case pressure of handgun ammo....

Case pressure with straight walled handgun brass is not always a constant. Thin walled vs. thick walled brass can make a difference.....mainly because it may change the case neck tension on the bullet. If the expander die for your caliber does not allow a good fit to provide good case neck tension on a thin walled piece of brass, there is a good chance you may encounter slight bullet set back which can drastically increase the pressure. We may not notice the difference when shooting a rapid string, but using a chronograph may show widely fluctuating velocities and possibly a lack of good accuracy.

I don't bother to check case wall thickness for handgun ammo, and I pick up brass at my local range that is probably not always mine....I simply tumble my brass and then reload.

However, if I want to work up a load for max accuracy, I always use new or once fired brass, and a good quality JHP bullet, like the Hornady XTP. The tension on the bullet in the case is probably more consistent with new brass, and the pressure curves are probably more consistent as well.....finding the right combination of powder and bullet for any gun is always the goal....! I have different loads for accuracy for different reasons. A mid range load may be fine for IDPA competition, but I may use a different powder to boost velocity while still maintaining optimal accuracy for a self defense load....that is the beauty of reloading....you have the ability to tailor the loads for your specific needs for your specific gun!

 

I would think that chronograph your loads, and comparing that to known load data FPS would be a good approach.
If your reloads are going a lot faster, you might be in an over pressure situation.

 

Interesting topic, thanks for all the replies. Keep 'em coming.



Only issue I see here would be that you can use a slower burning powder, to achieve higher velocities without approaching pressure limits. An example would be magnum pistol powders vs. fast burning shotgun powders in say your 357/44mags. You'll never achieve H110/W296 velocity with clays, but you can approach the pressure limit with the same bullet at a much lower velocity.

 

No; I have only blowed up one.

 

He shoots 9mm major... You just factor in the cost of a new open gun every so often when you do the math on how much cheaper 9mm brass is compared to 38 super.

 

Actually, ALL the Major 9 I've shot has been from my pair of EAA Witnesses.
When I shoot Open I (normally) install a 9x21 barrel with a factory two-port comp, load 9x21 brass, and draw it from a Yaqui Slide.
Just like when I wear it concealed.....

 

Explains some my crappy percentage.

 

Great dialog guys that's why I never stop learning on this forum!