Comparison of various SP and SR primers in the 357 Magnum

[charlie b]

Thanks Larry!

The data actually makes sense to me, given the load used.

I had always understood that the mag primers were intended for high load density powder loads (especially ball powders), which is kinda what Winchester implies with their primers. A bit more oomph for their line of powder. Using a mag primer in a lower load density should result in erratic ignition. I would expect the same from SR primers in pistols of lower load density.

By the same token, using std primers in high density magnum loads sometimes results in erratic velocities.

Too bad you don't have an 'expendable' barrel to use for such a test (high load density), since if there is an issue you would be far above safe levels.

The data is a great warning about using mag and rifle primers in many pistol applications.

[jeepyj]

Larry, Many thanks for such an Informative collection of information. With the current shortage situation I hear the primer question on a regular basis at the local LGS. I generally stay out of the conversation but listen with interest. This post has help me greatly with my understanding. Your patience and thoroughness of your answers to each of the questions presented is also a big help. Thanks again, jeepyj

[megasupermagnum]

Thank you very much for another great comparison Larry. These tests are always informative, and very much appreciated.

I will disagree slightly on your stance of not using large rifle primers. I look at that data, and I don't see a huge difference from a safety standpoint. According to SAMMI, the max average pressure is 35,000 PSI for 9mm Luger. SAMMI also describes maximum extreme variation as 4% standard deviation (MAP * 0.04) * (5.16) = MEV

I guess 5.16 was plucked from some unseen table, but they say it applies to all calibers. 35k * .04 = 1,400 and 1,400 * 5.16 = 7,224

So according to SAMMI, the pressure spec on standard 9mm Luger is 35,000 PSI + or - 7,224 PSI. That means according to SAMMI, a single sample of up to 42,224 PSI is of no concern, and meets their criteria for safety.

[dougader]

Excellent work Larry. Thank you for taking the time and sharing it here.

[JeffG]

Great information Larry. Thank you.

[Larry Gibson]

Thank you very much for another great comparison Larry. These tests are always informative, and very much appreciated.

I will disagree slightly on your stance of not using large rifle primers. I look at that data, and I don't see a huge difference from a safety standpoint. According to SAMMI, the max average pressure is 35,000 PSI for 9mm Luger. SAMMI also describes maximum extreme variation as 4% standard deviation (MAP * 0.04) * (5.16) = MEV

I guess 5.16 was plucked from some unseen table, but they say it applies to all calibers. 35k * .04 = 1,400 and 1,400 * 5.16 = 7,224

So according to SAMMI, the pressure spec on standard 9mm Luger is 35,000 PSI + or - 7,224 PSI. That means according to SAMMI, a single sample of up to 42,224 PSI is of no concern, and meets their criteria for safety.

The MEV [Maximum Extreme Variation] is not a +/- figure. It is based on the SD of the "population" [that is the SD of the load tested] x the constant of 5.16. Quoting the definition from SAAMI: "The MEV is the maximum allowable sample E.V. (Extreme Variation or range) is a statistic derived from the knowledge of the population Standard Deviation." Thus, unless you know the actual pressure SD of the load tested you can't compute the MEV. The use of the MEV formula is to compare the SD to the ES of the measured pressure of a given population (load) which ensures the pressure variation is within normal computed variation. Note the MEV by being computed based on an SD and compared to the ES it is based on an "average" figure, not based on individual shot pressures.

I'm not sure where you come up with a constant SD of "7,224" for the 9mm?

As a general statement I would not "conclude" individual shot pressures of 42,224 psi [if that figure were correct] in the 9mm P to be of "no concern". In some handguns designed for those psi's, perhaps. However, in smaller handguns w/o integral feed ramps that may not be a wise combination. You may be getting away with it with the load and specific primer you are using in the firearm you are using it in but to say or insinuate such can be used as a general rule is not something I derive from the actual test data. Ergo, I would have some concern.

However, the question was not "can you use" but was a question of "can or should you substitute SP magnum or SR primers safely". Two different questions with most probably two different answers. Answering the question based on the actual test data I will stand by my previous conclusion; if you really must use SP magnum or SR primers in a small capacity handgun cartridge then use a starting load and just go with that. Attempting to "work up" to a previous velocity when SP primers were used can lead to higher pressures. That is what I would do and is what I suggest.

[megasupermagnum]

I would love to be corrected. The numbers I posted were what I calculated from what believe are stated by SAMMI. I'm not a statistics wiz, so it is very likely I am wrong. Here is what SAMMI says their definition of standard deviation is. They plainly state that MAP times .04 equals SD. Also stated, 4% variation is allowed.

Standard Deviation () - The Standard Deviation for each Maximum Average Pressure level is based
on a Coefficient of Variation of 4%. This 4% Coefficient of Variation is maintained throughout the
SAAMI pressure spectrum providing a realistic Standard Deviation for each pressure level. To
obtain the Standard Deviation for a particular MAP, multiply the MAP by 0.04 (i.e., 50,000 psi x
0.04 = 2,000 psi).


35,000 * .04 = 1400

I then took that, and used it to calculate that MEV number. Their definition is listed below.

Maximum Extreme Variation - The maximum allowable sample E.V. (Extreme Variation or Range)
is a statistic derived from the knowledge of the population Standard Deviation. Applying table
figures from the Relative Range Tables (Biometrika Tables for Statisticians) we calculate the
Maximum E.V. or Range as (population ) x 5.16 (table constant for sample of 10 at 99.0%
confidence level) i.e., 2,000 psi x 5.16 = 10,320 psi rounded down to 10,300 psi.

1400 * 5.16 = 7224

Unless I'm reading this wrong, according to SAMMI they are saying their recommendation for 9mm Luger has a MAP of 35,000 PSI, and allow a variance up to 7,224 PSI. I just noticed they state to round down to the hundred. Again, unless I'm reading this wrong, they say that as long as your pressure average is 35,000 PSI or lower, and you do not have any single readings over 42,200 PSI, you are within their recommendations, since SAMMI is voluntary.

I understand your concern, however, I just do not see any cause for alarm with using primers other than small pistol. I'm just some guy with no farther qualifications, so this is worth exactly what you paid for it. I have yet to see a pistol fail with a simple overload. It is always a squib (stuck bullet), double charge, or other extreme failure that would not have been prevented with a slightly reduced load.

[Larry Gibson]

megasupermagnum

It is likely you are wrong in several assumptions you make, as you surmise in your post.

Regards the Standard Deviation; your erroneous assumption is the SD as defined in the SAAMI definition you quoted is the same as the population SD mentioned in the definition of the Maximum Extreme Variation. They are two different SDs. One (the SD you quoted) is the maximum allowable deviation from the MAP. It is a simple +/- figure derived from the MAP X 0.04. Thus the acceptable +/- MAP of a 9mm P would fall between 33,600 to 36,400 psi resulting from any test of the population.

The SD used in the calculation of the MEV is derived from the calculated SD based on the actual measured psi's of a test. It is the mean deviation calculated from the average psi of the population (tested load). Unless you actually measure the psi of a sufficient sample of the population (10 shots is seemed an adequate sample) you will have neither the mean average of the psi along with the individual psi's from which to derive the SD used in the MEV formula. If you look at the psi SDs in the data you'll see none of them conform to the "MAP X 0.04" formula. They don't because they are a different SD for a different use.

The MEV also is not a +/- figure. The MEV is a psi "range" of which to compare the SD. Using the formula in the SAAMI definition of MEV will provide a psi "range" which the psi ES of the tested population should fall within. Note any of the psi SDs in the test data and use the MEV formula to compute the range of ES the SD should fall within. All fall well within the MEV which simply means they are fairly uniform but not necessarily "safe".

Your error is using the wrong SD to compute the MEV. Then misunderstanding the MEV to be a +/- psi figure to be added or subtracted from the MAP. It is not. Calculating the MEV based on the actual SD of the tested population merely gives you the range of which the measured psi ES should fall within. Useful information but not something to hang your hat on about using excessive pressure loads.

Using the SD from the definition quoted in the MEV formula has given you the erroneous psi figures from which you then compounded the error by misconstruing it as a +/- figure.

I am not telling anyone not to use them. I am just presenting factual test data. Many things we do on a daily basis are risky. We, individually, must decide how much risk we want to take. In my previous post I stated what I would do based on the data I have now if I had to. I don't. You are free to do as you want and to take whatever risk you please.

[megasupermagnum]

Thank you.

[SlamFire1]

Have you tested different lots of the same primer brands? Primers are a mix of components. there are allowable percentages in the mix, and the purity varies, along with the homogeneity. A Gun Club bud used to visit Government ammunition plants, he said primer cake is mixed by hand, and that the workers who made the most consistent primer cake received cash rewards. But, as he said, consistency is an "artifact". I got the idea winning was not random chance, but there was enough variability in the process, making the best was not guaranteed even if the worker did everything the same as his last winning lot.

It is quite possible, the next primer test, with different lots of primers, the results will be shuffled.

I am unaware of anything that the primer makers have put out about their process control, and their production standards. There is no particular reason to assume that slightly substandard lots are not shipped and sold, especially in times of panic, as what is going on right now.

[charlie b]

....It is quite possible, the next primer test, with different lots of primers, the results will be shuffled....

Or the results could be much worse than presented.

[ddixie884]

Great work as usual, Larry. Thanx for sharing the fruits of your labor............

[RJM52]

Great work as always and #13 answered the only question I had and that was what the effect be on a max load of a slower burning powder...

As we have discussed in the past, I have been running many .38 Supers since 1980... All of my high performance loads run with Small Rifle powders. Doesn't seem to have hurt anything and accuracy is always astounding...

Bob

[Hi-Speed]

Lyman’s latest 357 Magnum load data lists using CCI550 magnum primers with all its powders including Unique. Their 158 gr jacketed HP loads using Unique starts at 6.4 grs (CUP 18,900) and max 8.3 grs (CUP 38,300)…

Lyman also shows cast data using Bullseye up to 7.0 grs with 155 gr 358156GC SWC again using CCI550 primers.

Lyman also recommends the same CCI550 magnum primers for their 357 Mag loads using 2400.

Edited:

…removing my speculations and just going by what published load data recommends.

I have nothing but the best to say about Larry Gibson and all his fine work that he has done on behalf of our great forum. I always look forward to his very informative and analytical posts.

“Start Low, Work Up”

[David2011]

Larry, your posts are always worth reading. Thank you! The data regarding SR primers, pressures in particular, is noteworthy. I never challenged the published data other than to use a different brand of the recommended size primer. My loads are rarely near the top anyway, other than Ruger/Contender only loads for .45 Colt and .44 Mag. The folks that publish reloading data have far better equipment than my lowly Competition Electronics chronograph. Best to believe what they write.