Pressure Data in Manuals

I was talking with a older reloader today and we were talking about a 10mm reloading project we plan on doing in the future. We got to comparing pressure values. Later I was looking at my data library and it came to my attention. Speer #14, Alliant 2014, doesn't include pressure values. While Hodgdon 2019, Western Powders, (year escapes me), Lyman#50 all include pressure data. I imagine this question has been asked before but does anyone know why the above mentioned sources quit including the information in their publications?
Having never actually seen QuickLoad in operation, but from my layman understanding where does the software get the pressure values if powder companies aren't publishing the information? Thank you.

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QL is an educated "guess". Values are not absolute, but a reasonable approximation of what you might expect, and is better than a wild guess. I would not take QL as gospel, but is is better than having no freaking idea and going entirely by guess and by golly!

Lyman 4th cast bullet manual simply states "where no pressure readings are shown, we did not take pressure readings and focused on powder charge"

IN other words, showing you the pressure reading for a particular loading, MAY cause you to wet your pants, Or they simply did not take it, or got to much variation between shots that it wasn't worth the time.

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Originally Posted by Outpost75

QL is an educated "guess". Values are not absolute, but a reasonable approximation of what you might expect, and is better than a wild guess. I would not take QL as gospel, but is is better than having no freaking idea and going entirely by guess and by golly!

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Outpost75 is correct, QL is only a guess that depends on how much data you input and how correct that data is. Much the same as the old Powley Computer. Most data in the latest manuals of those companies that actually test their own loads has been pressure tested and found to be with in SAAMI or "safe" limits with their own test fixtures/guns. Manuals that plagiarize data from other sources are, in my opinion, questionably reliable. The manuals admonition for you, the reloader, to start low and work up always applies. Far too many just assume the top end load will be safe in their firearm. That is not always the case......always start low and work up looking for pressure signs.

It’s generally not what the gun will take but what the brass will handle. More importantly what your brass will handle in your gun. Doing your own work up is best, working your way up watching for pressure, preferably over a chrono.

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Originally Posted by RedHawk357Mag

... does anyone know why the above mentioned sources quit including the information in their publications?

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Sorta. I mean no one I know of has said "...this is why" but understanding and reason can give us a solid clue for why they don't. People (us) want to KNOW what's going on when we work up our loads so printed pressure is very helpful data --- unless it's wrong; then it can be very wrong! Professional reloading testers can tell us what powder they used and what pressures they got in their test rigs but they can't tell us what the same load will do in OUR rig.

Following other people's pressure can be catastrophic if the differences go in the wrong direction. Book data cannot be anything but what it is and what it is is what other people have found true for themselves. Therefore each of us MUST do our own careful load development[/I] and stop when over pressure signs occur no matter what some book makers say was safe in their tests.

Load development is exactly that, a development in our own rigs and using our own components; no one else can safely do that for us. For more than 50 years now I've paid little attention to maximum book loads and no attention at all to any book COL or pressure tests -- and, for tens of thousands of rounds loaded for at least three dozen firearms, I've not had a single safety instance.

The 2019 Hogdon reloading manual does give pressure readings for start and max charges. I usually get one each year just to see if the data for a couple cartridges has changed. But I also have reloading manuals going back to the 70's and most of the Lyman manuals, Sierra, and a couple all have pressure readings. But those readings were done using pressure barrels or commercial or military firearms. Which would introduce variables all of their own. That's why they always say start at the start charges and work your way up observing for pressure signs. Frank

Well after a discussion with CIP customer service last year, CIP uses a different type of sensor then SAAMI, another reason they say the pressures are different.

Thanks everyone who weighed in on this.

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Pressure data is only relevant in the identical test barrel, temperature, and with the exact components including lot numbers and crimp. Close only works with horseshoes.

Most people reading pressures in loading manuals don't understand is that Pmax (machine loading limit) is based on the sample average plus 3 standard deviations, not exceeding the SAAMI MAP.

Having only the sample average published in the loading manual is misleading, because if that value given is substantially lower than MAP (X-bar + 3 Sigma) people are sometimes tempted to increase the load, which is particularly dangerous if that particular combination has a large shot-to-shot variation in pressure and velocity.

Outpost75

I think you're close to correct. I think most people just don't have clue about cartridge pressure and the measurement there of. I'm constantly amazed at the number that believe every factory or milsurp cartridge produces the MAP for the cartridge. Also how many think SAAMI MAPs and maximum listed loads are products of lawyers so it's okay to increase loads........

Larry,

Both the military and commercial industry changed test methods and the statistical conventions when they changed over to piezoelectric presure measurements. Everything commercial in my time was fired radial copper, except for some government contract work. When I was at Ruger we had Boots Obermeyter made dual-mode barrels in 9mm and .357 for Customs and Border Patrol which would permit both conformal transducer and radial copper on the same barrel. To get reliable piezo readings we had to fire separate strings because if the radial copper piston hole wasn't plugged, the gas loss from the case rupture would drop the psi readings and made for some squirrley p/t curves. That was the end of the dual-mode barrel. Tried to tell them it wouldn't work, but their bean counters thought they could save a nickel having only one barrel and getting two sets of data on one sample. Ha!

Was most interesting at the time because we were testing proof loads in both calibers.

The Army then was using either BRL Minihat and Kistler conformal transducers with drilled cases, so that you didn't need to correct for the differences in blanking pressure between a brass, steel or composite case. In 9mm and .45 the transducer was located near the case mouth and NATO went with the CIP standard, and I guess eventually SAAMI did too.