Home Forums Hunting & Shooting Ask The Gunwriters Who Set Max Average Pressure For SAAMI Cartridges?

Well, one thing is certain...my old GTG is not a comprehensive source for research.

I thought Redneck considered the Remington 740 series of rifles the finest deer rifles ever invented.

Apparently many shooters/hunters have no real idea of SAAMI, whether what it is, or the procedures for getting a cartridge accepted. It was started in 1926 at the urging of the federal government, because so many companies used their own dimensions and pressures when manufacturing both firearms and ammunition that problems occurred. This is why it's named the Sporting Arms and Ammunition Manufacturers Institute. (Europe has a similar organization called the CIP, which often sets similar standards as SAAMI.)

Generally SAAMI members meet once a year, to consider new cartridges and standards, from what I understand usually at the SHOT Show. When the individual member companies submit new cartridges, or new standards for older cartridges, they generally propose a pressure limit, but the entire organization decides on whether to accept those standards--along with chamber dimensions, etc.

So far no rifle cartridge has been approved for a maximum average pressure (MAP) of over 65,000 PSI, as measured by piezo-electric equipment under standard SAAMI conditions, which are described on their website. This is because even with modern powders resulting in far less temperature-variation in pressure, wide variations can still occur due to various factors beyond temperature, including bore and throat dimensions, fouling and even stuff like atmospheric moisture, which can turn into ice. (Variations can even occur in a temperature/humidity controlled pressure lab. I have spent considerable time in one where one guy in particular could "pull the string" on a piezo barrel so hard that pressures consistently averaged at least 1000 PSI higher than with any of the other techs.)

Consequently SAAMI prefers to leave some safety margin their rifle MAPs, the reason 65,000 PSI is the maximum ever approved--though I know of at least one manufacturer who wanted their new cartridge approved at 70,000 PSI--which was voted down. Instead it was approved at 65,000.

This is also why some ammo/rifle manufacturers don't belong to SAAMI. I know of one where their ammo regularly produces at least 70,000 PSI under standard SAAMO conditions, in their own rifles, and sometimes closer to 75,000 PSI. The owner of the company claimed the high velocities of his cartridges, in his rifles, were due to a magic case-shape--but independent testing proved they were due to 70-75,000 PSI pressures. (Generally so-called "pressure signs" many handloaders regularly use don't start to occur until at least 70,000 PSI.)

SAAMI standards are also voluntary among members. This is why some ammo eventually got loaded to what are known as +P pressures--though some of those were eventually approved by SAAMI, though only when labeled +P.

Lower MAPS are often imposed for cartridges that originally appeared long ago, before SAAMI was organized, partly due to the possibility of modern ammo being fired in older firearms. These might be made on weaker actions, but often were wildcats with variable chambers, especially throat length, which can cause big variations in pressures. This is why the .30-06's MAP is only 60,000 PSI, and even the .257 Roberts +P MAP is 58,000. It's also probably why the .35 Whelen's MAP is 62,000.

But after peizo-electric pressure testing became standard, some of the original copper-crusher SAAMI pressures (CUP) were also reduced, because piezo testing showed the pressures oinsome cartridges varied considerably more than indicated with copper-crushed equipment. Some individual rounds measured way above the CUP MAP, so standards were reduced until all rounds measured within what SAAMI considered a safer limit. Among these cartridges were the .243 Winchester and 7mm Remington Magnum, one reason their factory-listed velocities were reduced considerably after piezo testing became the standard. (The other reason is that SAAMI also decided to standardize test-barrel lengths. Before that occurred, many companies used 26-inch test barrels, when most factory rifles had 22-24 inch barrels.)

I have written even more extensively about this elsewhere, including some of my experiences when visiting various pressure labs. But those are the basics.

You should add that SAAMI is not a legal entity. There is no need for any business to comply with any limits agreed upon by SAAMI members. CIP, on the other hand, sets legal standards which must be followed by its members.

Thanks JB.

So, what you say about the .243 and 7 Rem Mag above kind of undermines some things I've felt or believed about them for some time, and that is that there is something "weird" or inherently unfortunate about their designs that causes a certain amount of unpredictability. What you're saying, IF I understand your meaning, is that there was nothing of the sort "wrong" with either cartridge, but rather it was discovered that they didn't perform the way we believed they did, and only because of [much] less than perfect measurement techniques. Is that on track?

For SAAMI, these items are discussed at different times - sometimes years apart - by various manufacturers. Generally speaking, pressure levels are recommended by the manufacturer who designed and tested them. Discussion might ensue.

There is no universal standard.

What sets those two cartridges apart is newer measurement techniques revealed irregularities that didn't occur with other cartridges examined with the same new techniques. So there is something a bit off about them.

So you're saying it's more difficult to keep everything "within the lines" when it comes to standard deviation and that sort of thing...am I correct?

I hadn't looked at this site in a long time, but if memory serves me they claimed that they knew some clever tricks in cartridge design (and maybe they really did---or do).

https://superiorballistics.com/

I'll have to take the time to look the site over. It appears to have changed somewhat since 2006 or thereabouts.

mathman,

I was visiting the pressure lab at a major ammunition factory, along with a couple other writers, when the ballistician leading the tour mentioned that .243s had "blown more barrels off of actions in pressure labs than any other cartridge." He said it primarily happened with lighter bullets, but almost never with 100-grain bullets.

A powder-distribution company started their own piezo lab years ago, in order to test powders they were having made in various places. (Most powder companies don't make their own powder. Instead they have it produced by various companies.) The guy they hired to run the lab was a long-time rifle loony who worked briefly with copper-crusher equipment while working for a bullet company years before, but had no previous experience with piezo equipment--but the company was also a distributor for a couple other well-known brands, and their folks offered to provide advice. He started getting wide-spread readings with the 7mm Remington Magnum, so called the powder companies, who said yeah, that's common with the 7MM RM.

The head of the pressure department at a major rifle company mentioned to me that all sorts of weird pressure stuff can happen when test-barrels start to erode. Sometimes pressures drop--but sometimes they increase, often erratically. He also confirmed that the .243 often caused problems.

There was a bullet company's pressure lab which used strain-gauge equipment, which when applied correctly produces just about identical results as piezo equipment--which is why several bullet companies use strain-gauges, since they cost a lot less than piezo actions and barrels. But the guy who ran the lab often got weird results, which he apparently thought were trustworthy. Among others, he claimed the .257 Roberts Ackley Improved got the same velocities and pressures with less powder than the .25-06. Have talked to a lot of other pressure-lab guys who said they'd never seen anything like that, with any cartridges--despite claims of ballistic magic concerning shoulder-angles and various other factors. Instead they all claimed velocity and pressure correlated directly with powder capacity--though some cartridges did tend to produce more consistent velocities.

Also know two guys who ran major pressure labs for decades, one for a powder company and one for a bullet company. One claimed that X large-rifle primers and Y small-rifle primers resulted in the most consistent results. The other claimed two completely different brands of LR and SR primers were most consistent. Both are now retired, and I never asked for more details from either, which is probably just as well.

Obviously there are still a lot of mysteries.

Well, until now. The new .277 SIG FURY has a SAAMI MAP of 80,000 psi.

But they added this warning to the drawing:

Superior Balistics is an interest site

1911a1

My comments regarding the 740 was not a condemnation of the 742, 7400, 74, or Four, just the 740. The problems Remington had with the 740 had to do with how fast they failed and the inability to rebuild them. Remington only made the 740 from 1955 to 1959, replacing them with the much improved 742.
I believe a bit of complaints regarding Remington’s semi-autos can be blamed on the 740. Other complaints may have come from inappropriate loads or lack of cleaning and lubricating.
I’m a little surprised that Redneck thought highly of these semi-autos - learn something every day.

"Much improved"??? LMAO... What a pos..


He was joking... Here's his post from my letterbox:

[You might want to visit the ask the gunwriters sub forum thread about Sammi numbers.

I jokingly replied that you thought the Remington 740 series rifles were the the finest deer rifles to be had. Ha Ha [/quote]

The Rem semi-autos were some of the worst semi-auto rifles ever... After more than 20 years working with those things I learned very well that the LAST rifle I'd ever buy would be a Rem semi-auto..

If someone really wants/needs an autoloader centerfire they'd be well-advised to obtain a Browning BAR.. At least those WORK!!


Education session over..

That's pretty strong since it puts the Remington beyond even the Winchester 100, another favorite of yours.

The Rem semi-autos were some of the worst semi-auto rifles ever... After more than 20 years working with those things I learned very well that the LAST rifle I'd ever buy would be a Rem semi-auto..

If someone really wants/needs an autoloader centerfire they'd be well-advised to obtain a Browning BAR.. At least those WORK!!


Education session over.. [/quote]

I suspected as much.

I'll have to disagree with your evaluation of the after 740 Remington Semi-autos since I never had a problem with mine. My experience was with the 742 and the 74. I hated chasing brass, so they eventually went down the road. They were accurate and I treated them right. I had a Winchester 100 and I felt that rifle was inferior to the Remington's, though it was a handy little rifle. I also had a couple variations of the Ruger 44 Mag semi-autos, which were fun. Other Semi-autos I've had experience with - M16, M14, M1, AR-10, and AR-15 of those I liked the M1 and the M14 the most.
I believe that the Browning BARs were good rifles. Perhaps the Remington rifles were fussier regarding ammo, IDK? Like I said I never had a problem with my Remington 742 or 74. I had a friend who had only one center fire rifle, which was a Browning BAR 7mm RM and he hunted an awful lot with it. He only shot factory ammo in it, so chasing brass wasn't a big deal for him. Deer, elk and pronghorns was what he shot with it. (I don't think he went to Africa with his Browning, but after he retired, I have lost touch with him.)

Would the real Saami please stand up? I still don't know who he/she/it is.

I suspected as much.

I'll have to disagree with your evaluation of the after 740 Remington Semi-autos since I never had a problem with mine. My experience was with the 742 and the 74. I hated chasing brass, so they eventually went down the road. They were accurate and I treated them right. I had a Winchester 100 and I felt that rifle was inferior to the Remington's, though it was a handy little rifle. I also had a couple variations of the Ruger 44 Mag semi-autos, which were fun. Other Semi-autos I've had experience with - M16, M14, M1, AR-10, and AR-15 of those I liked the M1 and the M14 the most.
I believe that the Browning BARs were good rifles. Perhaps the Remington rifles were fussier regarding ammo, IDK? Like I said I never had a problem with my Remington 742 or 74. I had a friend who had only one center fire rifle, which was a Browning BAR 7mm RM and he hunted an awful lot with it. He only shot factory ammo in it, so chasing brass wasn't a big deal for him. Deer, elk and pronghorns was what he shot with it. (I don't think he went to Africa with his Browning, but after he retired, I have lost touch with him.)[/quote]


I didn't mean to throw Redneck under the bus. I was being sarcastic. I figured it was well known about his disdain for Remington auto rifles.
I call them Wound-a-matics myself.

It is my understanding that within practical limits, the one who presents the proposed 'new' cartridge to SAAMI is the one who sets the limits. For instance when Lapua brought the 6.5 x 47 to the table the pressures indicated were at typical magnum levels (above 65,000 psi). Most don't realize that the small primer case is part of that design being stronger in the base and web area than if the case were a LR primer case. From a practical sense, this does protect the subsequent manufacturer of the ammunition from liability from both rifle manufacturers and users since the ammunition was designed and standardized before the intended firearms were produced. No doubt that if the 7mm & 8mm Mausers, the 250/300 Savages, and similar early cartridges were proposed to SAAMI after it was established in 1926, they would see much more popularity in addition to more robust loadings in commercial ammunition.

Belated, but perhaps useful:

SAAMI is a shield for ammunition manufacturers. "I made it to SAAMI specs."

P O Ackley wondered in one of his books how the specs were set, since they are so internally inconsistent. I think the basic fact is that we are all the canaries in the coalmine. If users are not experiencing failures using SAAMI specs, then the load is probably alright. Note that for a few decades, it was believed that CUP measurements reflected actual PSI. But 50 KCUP is really about 62 KPSI, so most bolt thrust calculations done in that period were well off the mark.