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Thread: Comparison of various SP and SR primers in the 357 Magnum

  1. #1
    Boolit Grand Master


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    Comparison of various SP and SR primers in the 357 Magnum

    Comparison of various SP and SR primers in the 357 Magnum


    Given the panic buying, hoarding and shortage of firearms, ammunition and reloading equipment and components several recent threads have asked if it is “safe” to use, in lieu of standard SP primers, magnum strength SP primers or even SR primers. This question pops up every now and then but the recent numerous queries on this topic seem to be driven by the dire shortage of primers. Some reloaders have no standard SP primers with no prospect of obtaining any in the foreseeable future at anything resembling a reasonable price. They do, on the other hand have SP magnum or SR primers both of which fit the primer pockets of handgun cartridges using a SP primer.

    A recent video by a small ammunition manufacturer indicated switching from a standard SP primer to a SP magnum primer of the same manufacture posed no problem in the 9mm P cartridge with the given load tested. They tested, on the video, two 3 shot tests of a load to get three shot tests of pressure and of velocity. While there appeared to a mild increase in psi and velocity when the SP magnum primer was used with the same load the difference did not seem to be too much. The factory rep so stated it was safe to substitute primers. I had reservations about that conclusion as the test sample was too small and the load (powder and charge) was not given. Now he could have done that test numerous times to get a valid test sampling but that was not apparent from the video.

    While I had not specifically tested a direct comparison between different types of primers I had, from previous chronographing and pressure measurements, formed an opinion that, while some switching of different makes and types of primers seemingly made little difference, switching primers can sometimes give sufficient differences, particularly in pressure. I, of course, referring to small handgun cartridges using the faster burning powders. The results of this test should in no way be construed as a blanket statement or rule of thumb. There are just too many variables concerning the volume of cartridge cases and, probably most importantly, the ignition and burning characteristics of slower burning powders. The results of this test apply to the use of the easily ignitable fast burning powders used in small handgun cartridges.

    Thus to find an answer to the question [Can SP magnum or SR primers be substituted for SP primers in the smaller cartridge cases with a given load?] I rummaged through my supply of SP and SR primers and came up with five different SP primer make/types to test;

    CCI 500
    Federal 100
    Winchester WSP
    CCI 550
    Federal 200 Magnum

    I also came up with five SR primer make/types to test;

    Remington 7 ˝
    CCI 400
    Winchester WSR
    Federal 205 Magnum
    CCI 450

    While there are other such primers I feel a sample of 10 different primers should give us an idea of the potential pressure increases and some aspect of whether or not substituting primers might be “safe”.

    Thus with that selection of primers I prepped 100 Winchester 357 magnum cases [ten shot test with each primer] . I selected a load to use with all the primers that was a mid-range 357 magnum load [based on previous chronographing] which should give a bit of “fudge” room if the psi’s did get too high with any primer. The load I selected to use was 6 gr of Alliant Unique under a 358156 cast of COWWs + 2% tin, sized .358, Hornady GCs crimped on and lubed with BAC. The bullets were seated, and roll crimped in the front crimp groove giving the loaded OAL at 1.597”.

    The SAAMI MAP for both the 357 magnum and the 9mm P are 35,000 psi.

    The test firearm was my Contender 7.94” barrel with the strain gauge located over the chamber as per SAAMI specification. The strain gauge was connected to the Oehler m43 PBL. Test conditions were a reasonable 60 degrees with 30% humidity and little to no wind. The velocity listed is muzzle velocity as the M43 corrects the screened velocity to the muzzle. The Oehler Sky-screen start screen was 10’ from the muzzle.

    All results are based on the 10 shot test string for each primer. All the time/pressure curves (traces) appeared normal for the test firearm. The results are listed by primer. Since the thrust of answering the question has to do with pressure that is the focus of this test. I shall make comments after the data for each primer is listed and also in conclusion.

    CCI 500 SPP primer

    Average velocity; 1178 fps, SD 11 fps, ES 38 fps. PSI average; 25,700
    SD 2,100, ES 5,700, high psi was 29,200 and the low psi was 23,500.

    This is a particularly good load. The internals are excellent as shown by the low SD/ES of both velocity and psi.

    Federal 100 SP primer

    Average velocity; 1189 fps, SD 10 fps, ES 36 fps. PSI average; 27,900, SD 1,700, ES 5,500, high psi was 30,300 and the low psi was 24,800.

    Another excellent load but we see a slight increase in velocity and psi. The 11 fps increase in velocity equated to an increase of 2,200 psi.

    Winchester WSP primer

    Average velocity was 1175 fps, SD 18 fps, ES 60 fps. PSI average; 26,300, SD 3,400, ES 9,900,
    high psi was 31,700 and the low psi was 21,800.

    This primer is supposed to be of stronger brisance as it is intended to ignite ball powders. We see a velocity and psi comparable to the previous two primers, but we also see a much larger SD and ES of both velocity and psi. Two of the tested rounds gave a psi above 30,000.

    CCI 550 SP Magnum primer

    Average velocity was 1179 fps, SD 17 fps, ES 60 FPS. PSI average: 27,500, SD 3,900, ES 13,500, high psi was 35,300 and the low psi was 21,800.

    This SP magnum primer showed no increase in velocity or in psi averages. However, obviously the internal psi created with what was supposed to be a “mild” 357 magnum load of Unique demonstrates something is amiss here given the somewhat erratic internal ballistics. Two the tested psi’s were above 30,000 with one exceeding the SAAMI MAP for the 357 magnum.

    Federal 200 Magnum SP primer

    Average velocity was: 1176 fps, SD 14 fps, ES 43 fps. PSI average: 27,100, SD 2,700, ES 8,800, high psi was 32,000 and the low psi was 23,200.

    Again, this magnum SP primer gave no increase in average velocity or psi. Yet the wide SD/ES of the psi measurements indicate somewhat erratic performance. The 32,000 psi shot gives cause for concern.

    Remington 7 ˝ SR primer

    Average velocity was; 1184 fps, SD 20 FPS, ES 78 FPS. PSI average: 28,100, SD 2,800, ES 9,100, high psi was 32,000 and the low psi was 22,900.

    Except for the much larger SD/ES of the psi this SR primer gave similar performance to the Federal 100 primer. We must note that two of the tested shots exceeded 30, psi with this primer but not with the Federal SP primer. A noticeable difference.

    CCI 400 SR primer

    Average velocity was: 1188 fps, SD 15 fps, ES 52 fps. PSI average was 29,200, SD 3,700, ES 12,200, high psi was 35,100 and the low psi was 22,900.

    Quite erratic yet the chronographed velocity does not indicate that. No appreciable gain in average velocity yet a 2-3,000 psi gain is apparent in the average psi. Five of the tested ten shots gave psi above 30,000 with one exceeding the SAAMI MAP.

    Winchester WSR primers

    Average velocity was: 1173 fps, SD 17 fps, ES 50 fps. PSI average was: 27,600, SD 3,800, ES 9,100, high psi was 32,600 and the low psi was 23,500 psi.

    Again, erratic internal psi yet not apparent based on the “normal “chronograph measurements. No appreciable increase in velocity or psi as shown by the “average” of each yet 4 of the tested shots exceeded 30,000 psi.

    Federal 205 SR Magnum primer


    Average velocity was: 1185 fps, SD 16 fps, ES 63 fps. PSI average was: 29,700, SD 2,400, ES 8,200, high psi was 34,000 and the low psi was 25,800.

    Again, erratic psi performance not belied by the chronographed velocity measurement. Three of the tested shots exceed 30,000 psi with one approaching the SAAMI MAP.

    CCI 450 SR primer

    Average velocity was: 1171 fps, SD 15 fps, ES 47 fps. PSI average was: 28,000, SD 2,400, ES 6,900, high psi was 31,000 and the low psi was 24,100.

    No gain in velocity, small gain in psi with three of the tested shots above 30,000 psi. Appears to be the mildest of the “magnum” strength SR primers tested.


    So there’s the data which brings us back to the question: is substituting a SP magnum primer or a SR primer for a standard SP primer “safe” in a small handgun cartridge? The answer is somewhat of a conundrum. If the load with the standard SP primer is a low or mid-level load then the substitution may be deemed “safe” depending on the actual case capacity of the load in question. But then, how do you know?

    Unless you can measure the pressure, you won’t know. Dropping back and working back up to the same chronographed velocity is often recommended. I have even recommended that myself in the past. But is that safe? Looking at the velocities of all ten tested primers with the same load we find the average velocities ran from 1171 fps to 1188 fps, a spread of only 17 fps. Interestingly the lowest and highest velocities of any of the rounds shot were with SR primers. The average velocity variation falls easily within the average to average variation we can get chronographing the same load several times.

    Thus chronographing really isn’t going to give an indication of the difference in psi. The three standard SP primers averaged 25,700 psi to 27,900 psi with the highest psi of any individual shot being 31,700 psi. With the SP magnum primers and the SR primers the psi was always higher with several of the tested shots exceeding the SAAMI MAP of 35,000 psi. If we ponder what the highest tested shot psi’s would be (not the average of the test) if we had used a max load developed with standard primers in the 34-35,000 psi and then had substituted the standard primer with a SP magnum or SR primer? The highest shot psi’s would probably have exceeded 40,000 psi. That would not be what I consider to be “safe”. Might get away with in in some larger framed revolvers but still not something to be recommended. In a semi auto you might get away with it but it would beat the gun up at best and if a case head burst at the web.......possibly disasterous.

    In the 9mm P with its much smaller case capacity? I would not use any other primer than a standard SP primer with other than a "starting load".
    Last edited by Larry Gibson; 01-29-2021 at 03:24 PM.
    Larry Gibson

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    Boolit Grand Master



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    Larry thanks for the very detailed and informative post.
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

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    wow... well there goes that theory!!!!

    nice work Larry
    Any technology not understood, can seem like Magic!!!

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    Boolit Master
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    Very interesting , thank you for posting and doing the tests .
    It would be interesting to know if a slower powder like 2400 that is often loaded with both standard and magnum primers would show similar results .
    I have compared velocity of some 9mm loads with ( BE-86 ) both magnum and standard primers same load except for primers , and we decided there was not much difference 50 to 70 FPS , now I know we have no idea what was going on pressure wise.
    Thanks again.

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    Boolit Buddy

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    Thank you Larry for the information! I would have never thought there could be that much variance in pressure without change in velocity.

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    Boolit Master
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    With the SAAMI MAP of 35,000 psi. did any of the over presure loads are any of the primers showing visible signs of overpressure ?

    Q
    if we started at min loads and worked up .. do you think we would have problems

    Most of my shooting is just putting holes in Paper and I very rarely shoot near max

    When I was shooting IPSC was the only Time I pushed it was in the 40 but the primers never showed any excessive signs (reg pp)

    Practice was a low to med load of a different powder

    I do have some CCI SR that I had Planed to shoot in 38 special / 357 target loads

    switched to SRM for all of my 223 / 300 bo ar Loads .... harder primer

    Thanks for expanding our knowledge base

  7. #7
    Boolit Grand Master


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    Very well done

    BTW, I always cringe when someone alludes to using a chronograph to check the safety of a load. Anyone who believes that should read Larry’s post until they understand it.

    One small point Larry, did you notice any discernible differences in primer deformation when there were 10k+ differences in the same load?
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    Boolit Master

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    Nice work Larry.
    The test is up to your usual high standards.
    Very few of us have pressure testing equipment so the chronograph is not telling us when the pressure is high.
    I always assumed that if the pressure increased the velocity would show it. Guess not.
    I have always thought the flatness of a primer was sign of pressure.

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    dale2242

    None of the primers exhibited any sign of excess psi. All the fired primers were very similar in appearance. Flatness of primer can be an indication of pressure if the cartridge to chamber headspace is not to great. that is when the primer backs out initially then is flattened as the case is driven back over it to the breach face. Also consider the flatness of the primer indicates psi only. The primer may appear to be flattened from "high pressure" but that's not necessarily the case. A primer with a softer cup will flatten more than a hard cup primer giving the appearance of excessive psi when, in fact, the psi is within normal limits for the cartridge. That's why primer flatness/appearance is no longer considered to be a reliable indicator of excessive pressure.
    Larry Gibson

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    Larry, thanks, excellent work as always. I had stayed out of the primer substitution discussion because I had very little data. The one data point I had was improved accuracy from substitution of small pistol primers in .22 Hornet. This is reinforced by your results, small charges of power don't seem to ignite as uniformly from larger primer charges. The rule of thumb seems to be use a strong enough primer but not too strong. I only sort of agree that you can't tell with chronograph results. The clues are there, the erratic ignition shows up as greater extreme spread and standard deviation for the stronger primers. You would not notice unless you had a good bit of old data to compare to when changing primers.

    I don't think substituting primers is dangerous, not dangerous like a double charge anyway. If you are someone who loads to max. you should probably back off if you switch primers.

    Your data is awesome as it gives us better understanding of the relative strength of each primer.

    I am not surprise by the lack of a velocity increase, the hotter primer does not add much to the total energy if you assume all the powder burns in all cases. These are either great loads you are a very fine handloader as these in my experience all these es and sd's are small.

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    Ford SD

    With the SAAMI MAP of 35,000 psi. did any of the over presure loads are any of the primers showing visible signs of overpressure ?

    No. As mentioned to dale2242, the primers all appeared essentially the same. Given proper headspace primer "flatness" does not really manifest itself until pressures get much higher.

    Q
    if we started at min loads and worked up .. do you think we would have problems


    Note the load I used was a "mid range" 357 magnum load with average psi in the 25 - 28,000 range no single rounds psi exceeding 31,700 psi. With some SP magnum and SR primers the average psi increased 2-3,000 +/- psi with many of the individual rounds psi near or exceeding the SAAMI MAP of 35,000 psi. Do I think you will have problems? I think, if you must use SP magnum or SR primers is small capacity handgun cases, that I would just go with the "starting" load and call it good. At least you're still shooting that way. Working up higher than a start load, probably depending on the cartridge, could get into unknown high psi's very quickly.

    Most of my shooting is just putting holes in Paper and I very rarely shoot near max

    When I was shooting IPSC was the only Time I pushed it was in the 40 but the primers never showed any excessive signs (reg pp)

    Practice was a low to med load of a different powder

    I do have some CCI SR that I had Planed to shoot in 38 special / 357 target loads


    All sounds good.

    switched to SRM for all of my 223 / 300 bo ar Loads .... harder primer

    I also use WSR or SR magnum primers in my 223/5.56 loads because of the ball powders I load with. Also the pressure levels for the firearms [ARs, bolt guns and SSs] run up into the 56 - 62,000 psi range. That rifle cartridge was made for those pressure levels. I don't shoot the 300 BO but shoot a bajillion 30 Carbine rounds. The use of standard SR primers [7 1/2s, WSRs and CCI 400s with top end H110 loads under cast or jacketed bullets works well. With sub-sonic loads using Bullseye powder a standard SP primer gives the most uniform velocities. Same in the diminutive 22 Hornet case, a SP primer works best giving the most uniform velocity and psi's with all powders I normally use [Bullseye, Unique, 4227, H110 and Lil'gun].

    Thanks for expanding our knowledge base

    You're welcome, my pleasure
    Larry Gibson

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    dtknowles

    "These are either great loads you are a very fine handloader as these in my experience all these es and sd's are small."

    Well, I certainly like to think I have, over the many years, become "a fine handloader". But, alas, the smaller ES and SDs in this test had more to do with the load used (it's generally been proven to be a fine mid-range 357 magnum load) and the test firearm. The closed breach of the Contender almost invariably gives more uniform ES and SDs than revolvers do with their attendant longer cylinder throats and barrel/cylinder gaps. But.....I certainly like to take credit......
    Larry Gibson

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    Boolit Grand Master


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    Quote Originally Posted by onelight View Post
    Very interesting , thank you for posting and doing the tests .
    It would be interesting to know if a slower powder like 2400 that is often loaded with both standard and magnum primers would show similar results .
    I have compared velocity of some 9mm loads with ( BE-86 ) both magnum and standard primers same load except for primers , and we decided there was not much difference 50 to 70 FPS , now I know we have no idea what was going on pressure wise.
    Thanks again.
    This may answer your interest;

    Test of Hercules and Alliant 2400 powder (14 gr each) in the 357 Magnum with a 358156 GC’d cast bullet using 6 different primers.

    All measurements were taken during testing conducted on 29 April, 2019. Data recorded with an Oehler M43 PBL using Contender 357 with 7.9” barrel. A 2 ˝ power scope was used on the Contender.

    Temperature ranged from 80 to 82 degrees.
    Humidity was 30%.
    Barometric pressure was 29.63.

    H2400 = Hercules 2400 manufactured in ’92.
    A2400 = Alliant 2400 of current manufacture (purchased 2 months ago)
    Velocity in fps is at muzzle.
    Velocity SD/ES is fps.
    PSI is the pressure (pounds per inch) recorded via the Oehler M43.
    PSI SD/ES is the pressure (pounds per inch) variation of the test string.
    Group = target at 50 yards with ctc measurement of 2 widest shots.
    All test strings were 10 shots.

    The 358156 were cast in a Lyman double cavity mould.
    Alloy was a soft one made of RL + Pb + tin.
    Bullets were AC’d 10+ days before size/lubing and BHN runs 10 – 11.
    Bullets as cast are .359+ and were size/lubed in Lyman 450 with .359 H&I die.
    Lube used was BAC.
    Hornady GCs were seated in the 450 with GC seater prior to size/lubing.
    The bullet weight, fully dressed, was 162 gr.

    All charges of both the Hercules and Alliant 2400 were 14 gr (+/- 0.1 gr).
    All test charges were thrown charges with a Lyman 55.
    Charges were verified between each 10 charges thrown on an Ohaus 10-0-5 scale.
    Cases were Winchester brass cases.
    Cartridges were loaded using RCBS dies on CH press.
    Primers are as indicated.
    Bullets were seated to 1st crimp groove (the 358156 has two) for an OAL of 1.597”
    A heavy rolled crimp was applied.

    Looking at just the H2400 data it would appear the old adage of “magnum primers not necessary” does apply. The average velocities between the various primers, standard and magnum, were found to be pretty consistent. The pressures are also consistent and all fall under the SAAMI MAP for the 357 magnum cartridge. However, the accuracy of the magnum primed loads was consistently better than the standard primers with the exception of the WSP primer with the A2400 powder.

    Looking at just the A2400 data we see pretty much the same consistence except the Alliant 2400 does appear to be somewhat faster burning than the older lot of Hercules 2400. In my previous testing I was using a lot of Alliant 2400 I purchased about 12 years ago. There was not the difference between that older lot of A2400 and the H2400 that we see here. Note also that this lot of A2400 consistently produced better accuracy than the H2400 regardless of the primer used. Interesting the highest velocity (1607 fps) and highest pressure (41,600 psi) produced the smallest 10 shot group. Additionally with standard primers the CCI 500 and WSP primers produced psi’s right at the SAAMI MAP. The Federal 100 produced a psi 3,400 more than the SAAMI MAP.

    Comparing this lot of A2400 to the old lot of H2400 shows a decided difference. This lot of A2400 is obviously faster burning giving 90 to 160 fps (+/-) difference depending on the primer used. The SAAMI MAP for the 357 Magnum is 35,000 psi and we see in Lyman CBH #4 the max load of 2400 with a CCI 550 primer is 14 gr. Looking at the test results the pressure with that load using H2400 is under the SAAMI MAP. But the pressure using this new lot of A2400 with the same load and same primer is 39,000…..well over the SAAMI MAP.

    So let’s answer the questions;

    “Would it make any difference using these primers with Bullseye, Unique, and Red Dot ?”

    Based on the large increase in psi over standard primers in this test it would appear the use of the Federal magnum SP primer would probably increase the psi significantly. If you really want to use those magnum primers then I suggest you drop the charge of any of those powders by 2 gr and work back up the same velocity as produced with a standard primer.

    “No Magnum primers with Hercules or Alliant 2400!” ………… “You are probably safe with Hercules 2400, but not Alliant 2400.”

    Based on this test it appears neither of those statements are quite correct. The use of a magnum primer and the WSP consistently proved more accurate than the standard primers with the same load. The remaining question seems to be if the load of A2400 is reduced to the SAAMI MAP Using any of the magnum primers will the accuracy be as good? Remains to be seen.

    ---Primer---------Powder----- Velocity----SD/ES-------PSI-----------SD/ES---------Group

    Federal 100--------H2400--------1425-------13/44-------31,000-------1500/4500-------5.45”
    ----------------------A2400--------1572-------16/46-------38,400-------1200/4000-------5.1”

    CCI 500-----------H2400---------1452-------12/41-------29,200-------1800/5200-------4.95”
    ----------------------A2400--------1551-------15/39-------35,400-------1500/5100--------4.87”

    Win WSP---------H2400---------1425-------16/60-------26,200-------2000/6900--------5.2”
    ---------------------A2400---------1536-------14/49-------34,800-------1200/4300--------3.75”

    Federal 200------H2400----------1481-------11/38-------32,100-------2500/6600--------3.7”
    Magnum---------A2400----------1566-------15/46-------38,900-------2000/5800--------3.15”

    CCI 550----------H2400----------1457-------11/37-------30,300-------2500/8900--------3.6”
    Magnum----------A2400----------1581-------17/51-------39,000-------2100/6400-------3.55”

    Winchester-------H2400----------1446-------22/67-------39,500-------2300/7000-------3.9”
    WSPM------------A2400----------1607-------12/37-------41,600-------2700/9000-------2.85”
    Larry Gibson

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    Boolit Grand Master Outpost75's Avatar
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    Outstanding work Larry, as always.

    I am looking forward to a future project we exchanged email about in loading the .32 S&W Long in +P to establish a safe loading limit for modern revolvers like the S&W Models 30 and 31 and also for use in revolvers chambered for the .32 H&R Magnum. I expect that with the small case at high loading density primer choice may also be significant there.
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    Boolit Master
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    Wow great information also in your post #13 thank you again Larry.

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    Nice work Larry, You have the CCI 500 primer listed as both SP and SR. They are SP primers. just a clerical mistake I am sure.

    Ken
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    Boolit Master
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    Much better info than the three 3 round tests done in the "recent video". Not only was that a very small sample size, but he got one round that was like 20% higher pressure than the others and says that it should just be ignored! When you do a very small sample and get an outlier like that, it should not just be ignored. Like your testing shows a 20% variation in pressure can happen and does happen.

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    Boolit Grand Master


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    Quote Originally Posted by Screwbolts View Post
    Nice work Larry, You have the CCI 500 primer listed as both SP and SR. They are SP primers. just a clerical mistake I am sure.

    Ken
    Thanks for the catch. That was under the primers to be tested. Should have been a CCI 450 primer (corrected). The test data was correct listed under the CCI 450 SR primer.
    Larry Gibson

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    Boolit Grand Master


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    Quote Originally Posted by reddog81 View Post
    Much better info than the three 3 round tests done in the "recent video". Not only was that a very small sample size, but he got one round that was like 20% higher pressure than the others and says that it should just be ignored! When you do a very small sample and get an outlier like that, it should not just be ignored. Like your testing shows a 20% variation in pressure can happen and does happen.
    Excellent and correct observation!
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  20. #20
    Boolit Grand Master


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    Some expressed interest in the flatness of the primers so here's the primers left to right columns as tested;

    Click image for larger version. 

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    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check