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SMALL PISTOL MAGNUM PRIMERS


glynnm45

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I have come into possession of 3000 small pistol magnum primers and am at a loss as to how/what to use them i.e. what loads? Right now I load 9mm and .380 auto. Are they O.K. to use in place of regular small pistol primers?

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Should be, they'll add about 10-15 FPS to your loads. It's all I use for 40, 38/357, and 38 super. Mainly, cause small pistol is so hard to find right now.

My experience was the same. A while ago I ran out of primers for my 9mm (this was during the period where primers were almost NON-EXISTANT) and a local shop got some in, but they limited buyers to 1,000 of each 'type' of primer. I bought 1k of SP and 1k of MagSP (the MagSP were almost $10 cheaper for some reason) hoping that the MagSP's would work out okay with my handload. Turns out, the difference between the two was barely noticeable. If anything, the MagSP's IMPROVED the accuracy of my load (by a small amount) and the only thing I noticed was a small difference in the way they sounded compared to the regular SP's. I had no pressure signs/flattened primers, no light strikes/failure to ignite, etc... In the future, I will (happily) purchase whichever variant is available, and if the MagSP's are cheaper guess which ones I will choose?

BTW: The SP's were CCI500's and the MagSP's were CCI550's.

-Kyle

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Should be, they'll add about 10-15 FPS to your loads. It's all I use for 40, 38/357, and 38 super. Mainly, cause small pistol is so hard to find right now.

My experience was the same. A while ago I ran out of primers for my 9mm (this was during the period where primers were almost NON-EXISTANT) and a local shop got some in, but they limited buyers to 1,000 of each 'type' of primer. I bought 1k of SP and 1k of MagSP (the MagSP were almost $10 cheaper for some reason) hoping that the MagSP's would work out okay with my handload. Turns out, the difference between the two was barely noticeable. If anything, the MagSP's IMPROVED the accuracy of my load (by a small amount) and the only thing I noticed was a small difference in the way they sounded compared to the regular SP's. I had no pressure signs/flattened primers, no light strikes/failure to ignite, etc... In the future, I will (happily) purchase whichever variant is available, and if the MagSP's are cheaper guess which ones I will choose?

BTW: The SP's were CCI500's and the MagSP's were CCI550's.

-Kyle

Thanks for the info, I'll try the SP mag primers if I find one.

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They fire hotter, so they can ignite more powder. Especially useful in magnum cartridges, or in larger volume cases.

They also normally have a thicker or harder (or both) cup material to handle the higher pressures often encountered with magnum cartridges. R,

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Thanks everyone for the information/advise especially G-ManBart. I guess I have a difficult time considering all these words in the same sentence : SMALL-MAGNUM-PISTOL-.38-9mm. The .357 would be the only one I would consider a small magnum pistol. I suppose when one talks about +P loads THEN we are talking magnum status. At any rate, I will use them in my 9mm without fear of harming my gun that's really all I needed to know.

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I have come into possession of 3000 small pistol magnum primers and am at a loss as to how/what to use them i.e. what loads? Right now I load 9mm and .380 auto. Are they O.K. to use in place of regular small pistol primers?

STOP - DO NOT use them! Send them to me for proper disposal. :roflol:

Seriously, you won't find them any problem for 9mm and I'm sure also for 380. I don't load 380 so I have no first hand experience but I do for 9mm.

Edited by tohlmann
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They also normally have a thicker or harder (or both) cup material to handle the higher pressures often encountered with magnum cartridges. R,

Are you sure? Not trying to be a smartass, this is just something that a lot of people seem to "know" is true. But when I switched from Federal 100 SPs to Federal 200 SPMs it really didn't seem to make a difference in my ignition reliability, even with a lightened firing pin spring in a Glock. Anyone who works at an ammunition factory - or has worked at one in the past - have a really definitive answer to this one? I'd be fascinated.

Guy?

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They also normally have a thicker or harder (or both) cup material to handle the higher pressures often encountered with magnum cartridges. R,

Are you sure? Not trying to be a smartass, this is just something that a lot of people seem to "know" is true. But when I switched from Federal 100 SPs to Federal 200 SPMs it really didn't seem to make a difference in my ignition reliability, even with a lightened firing pin spring in a Glock. Anyone who works at an ammunition factory - or has worked at one in the past - have a really definitive answer to this one? I'd be fascinated.

Guy?

I don't have anything definitive, so no. Still, on an anecdotal level, I've loaded both .40 and Super/Supercomp to Major with no other changes than the primers. For example, Win SP flatten much more than Win SR. So, something is different....they either have harder cup metal, thicker cup metal or a little bit of both since the velocity isn't significantly different (actually a touch lower with the SP). I've found the same thing with Fed SR, SP and SPM, although I haven't tried their SPM in .40 yet. Fed SP with my current 38SC load show a lot of flattening where the SPM have just a touch and the SR almost none...maybe actually none since they get a little flattening from being seated during loading. If the pressure is the same (relatively speaking) and one flattens/smears and the other doesn't it has to be some sort of difference in thickness or hardness of the cup material.

Regardless, I'd like to hear an insider's view if they're willing to talk about it. R,

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I guess my question really is one of definition: WHAT IS A SMALL MAGNUM PISTOL. Again, I can see a .357 being classed as a magnum pistol- small??? To my way of thinking, there are two types or classifications of pistols. There are small pistols and large pistols. Probably some of the Derringers are magnum, Charters Bulldog, ect. Was the "small pistol magnum primer" made for these guns?

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You are confusing the issue with small pistol/magnum primers. They are LARGE and SMALL primers. Each of those come in a regular or magnum variety. Just because its a small pistol magnum primer, does not mean that it is only for small pistol magnums (and doesn't mean it's for small pistols either! :rolleyes: ). And actually, a .357 is pretty small. It's .002 thousands of an inch bigger than a 9mm. It's the case that makes it a magnum, it holds more powder, so therefore you need a hotter primer to ignite the powder more efficiently, and also a harder cup to contain the greater pressures involved. Look at the .32 H&R Magnum, even smaller diameter bullet, but still a magnum. While the 45 ACP is a quite large semi auto round, which uses large primers, but it isn't a magnum, while a 45 GAP takes a small primer. A large primer is just that, larger in surface area than the samll primer. Then it gets even worse! A 40 S&W takes a small primer (whether it be a small pistol or small pistol magnum primer) where as a 10mm, which the bullet is the same diameter (the case is just a smudge longer), takes a large primer. And to further confuse, you can load the 40 S&W up to 10mm velocity in the shorter case!

By the way, the Charter Arms Bulldog is a 44 special (not a magnum!), and takes large primers.

Edited by GrumpyOne
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I have been using the Wolf SP mag primer interchangeably with the non mag Wolf primers in 9mm loads and have found them to work such fine. Normally the Mag primers would be a littler hotter but at least in my case haven't noted any velocity changes. They may be slightly harder because I had some problems with them in a Glock and a XD, both of which have very light trigger jobs with reduced power striker springs and normally require federal primers to be 100%. I haven't tried them in any revolvers yet.

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You are confusing the issue with small pistol/magnum primers. They are LARGE and SMALL primers. Each of those come in a regular or magnum variety. Just because its a small pistol magnum primer, does not mean that it is only for small pistol magnums (and doesn't mean it's for small pistols either! :rolleyes: ). And actually, a .357 is pretty small. It's .002 thousands of an inch bigger than a 9mm. It's the case that makes it a magnum, it holds more powder, so therefore you need a hotter primer to ignite the powder more efficiently, and also a harder cup to contain the greater pressures involved. Look at the .32 H&R Magnum, even smaller diameter bullet, but still a magnum. While the 45 ACP is a quite large semi auto round, which uses large primers, but it isn't a magnum, while a 45 GAP takes a small primer. A large primer is just that, larger in surface area than the samll primer. Then it gets even worse! A 40 S&W takes a small primer (whether it be a small pistol or small pistol magnum primer) where as a 10mm, which the bullet is the same diameter (the case is just a smudge longer), takes a large primer. And to further confuse, you can load the 40 S&W up to 10mm velocity in the shorter case!

By the way, the Charter Arms Bulldog is a 44 special (not a magnum!), and takes large primers.

Not really. :)

Small pistol magnum primers are intended for use in magnum cartridges that use small primers....357 Magnum, .32 H&R Magnum, the new .327 Mag, probably the .357 Maximum and some others I'm sure I'm forgetting like .38/55. Yes, in our sport(s) we use them for other than magnum cartridges, but that's pretty unique in the reloading world.

It's not the case that requires the magnum primer, it's the pressure and the amount of slow powder that might need to be lit that changes things. Magnum primers are more to contain higher pressures than they are to provide more/hotter spark although that is a side benefit. There are some huge cases that don't require magnum primers...like .45 Colt and 44-40...normal large primers work perfectly with them even though you can put a lot more slow powder in them than you can in a .357 Magnum. Even with the extra powder they're working at lower pressures than the .357 is, so they don't need magnum primers.

I'm not sure how much experience you have with the 10mm, but no way can you get 10mm velocities out of .40 cases. You can handload .40 to close to 10mm factory ballistics (some factory ammo), but you can load (and buy) some really hot 10mm that you'll never be able to match with a .40 case....normally an extra 100fps or more. I've shot Cor-bon 180gr Hunter 10mm out of my 610 3 7/8") and it was over 1200fps...in an auto it would be around 1300fps if the factory data is close. You won't get that with any .40 that's even close to within pressure limits. R,

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You are confusing the issue with small pistol/magnum primers. They are LARGE and SMALL primers. Each of those come in a regular or magnum variety. Just because its a small pistol magnum primer, does not mean that it is only for small pistol magnums (and doesn't mean it's for small pistols either! :rolleyes: ). And actually, a .357 is pretty small. It's .002 thousands of an inch bigger than a 9mm. It's the case that makes it a magnum, it holds more powder, so therefore you need a hotter primer to ignite the powder more efficiently, and also a harder cup to contain the greater pressures involved. Look at the .32 H&R Magnum, even smaller diameter bullet, but still a magnum. While the 45 ACP is a quite large semi auto round, which uses large primers, but it isn't a magnum, while a 45 GAP takes a small primer. A large primer is just that, larger in surface area than the samll primer. Then it gets even worse! A 40 S&W takes a small primer (whether it be a small pistol or small pistol magnum primer) where as a 10mm, which the bullet is the same diameter (the case is just a smudge longer), takes a large primer. And to further confuse, you can load the 40 S&W up to 10mm velocity in the shorter case!

By the way, the Charter Arms Bulldog is a 44 special (not a magnum!), and takes large primers.

Not really. :)

Small pistol magnum primers are intended for use in magnum cartridges that use small primers....357 Magnum, .32 H&R Magnum, the new .327 Mag, probably the .357 Maximum and some others I'm sure I'm forgetting like .38/55. Yes, in our sport(s) we use them for other than magnum cartridges, but that's pretty unique in the reloading world.

It's not the case that requires the magnum primer, it's the pressure and the amount of slow powder that might need to be lit that changes things. Magnum primers are more to contain higher pressures than they are to provide more/hotter spark although that is a side benefit. There are some huge cases that don't require magnum primers...like .45 Colt and 44-40...normal large primers work perfectly with them even though you can put a lot more slow powder in them than you can in a .357 Magnum. Even with the extra powder they're working at lower pressures than the .357 is, so they don't need magnum primers.

I'm not sure how much experience you have with the 10mm, but no way can you get 10mm velocities out of .40 cases. You can handload .40 to close to 10mm factory ballistics (some factory ammo), but you can load (and buy) some really hot 10mm that you'll never be able to match with a .40 case....normally an extra 100fps or more. I've shot Cor-bon 180gr Hunter 10mm out of my 610 3 7/8") and it was over 1200fps...in an auto it would be around 1300fps if the factory data is close. You won't get that with any .40 that's even close to within pressure limits. R,

While I agree with you in theory about the the first part, just because something says "Magnum" on the case, doesn't mean it is one. I mean, if that were the case, wouldn't we be shooting 38 super magnums? :rolleyes: While the .357 is a quite potent round, and you are supposed to use magnum primers, the 38 supers we shoot are even more high pressure than that, and the 9mm major is even more than the super. Even some factory loaded 38 super exceeds .357 pressures. I've been shooting my super with WSP primers almost exclusively, I see no flattening, primer flow etc. (at least to any worrying degree). Do you think that with the lower pressure of the .357 they would flatten and crater and flow with just a small pistol primer? I don't. If that were the case, wouldn't (and shouldn't) you be loading 38 special +P+ with a magnum primer? It is approaching standard .357 velocities, right? But the standard is to use the small pistol primer, not the magnum primer. Take the pressure of a .357 magnum. It is 35,000 PSI (per 38super.net pages) and the 40 S&W is also 35,000 PSI, but do you consistently load the 40 S&W with a magnum primer because of the pressure?

Table 2: SAAMI Maximum Average Pressure Standards

Cartridge psi* CUP†

25 Auto 25,000 18,000

32 Auto 20,500 15,000

380 Auto 21,500 17,000

9mm Luger 35,000 33,000

38 Special 17,000 17,000

38 Automatic 26,500 23,000

38 Super 36,500 33,000

9X23 Winchester 55,000** -

357 Magnum 35,000 45,000

40 S&W 35,000 -

10mm Auto 37,500 -

44 Magnum 36,000 40,000

45 ACP 21,000 18,000

Bear in mind that these are SAAMI specs for factory rounds!

There are some huge cases that don't require magnum primers...like .45 Colt and 44-40...normal large primers work perfectly with them even though you can put a lot more slow powder in them than you can in a .357 Magnum. Even with the extra powder they're working at lower pressures than the .357 is, so they don't need magnum primers.

The second part, well the bigger rounds you are talking about all have a bigger diameter at the primer, and although they may have more powder in the charge, they also have more surface area of powder touching the primer, so you are igniting more powder with the primer in a larger case (even with it being a regular large pistol primer) at the initial time of firing than you would be in a narrower case. Take for instance, Alliants reloading page shows a 158 grn .357 loaded with 8.5 grains of Power Pistol with a velocity of 1,078 FPS, while a 45 GAP shooting a 185 grn GDHP is loaded at 7.8 grains of the same powder, with a velocity of 993 FPS, and a 45 auto loaded with the 185 GDHP and 9.5 grains of of Power Pistol is pushing 1,047 FPS, but it is just a standard large pistol primer. The pressures between the 158 .357 load and the 185 grn 45 auto load would be about the same (heavier bullet, same powder, very close to the same velocity). The .357 has a case volume of 19.5 grains of H2O, while the 45 auto has a volume of 25 grains of H2O. (I probably just made your case, but after reading all this, now I'm confused! :rolleyes: )

As far as the 10mm goes, I should have said you can load the 40 S&W "close" to 10mm velocities in standard loads, but Winchester 10mm 175grn STHP is 1290 FPS and a 40 S&W 155grn STHP is 1205 FPS (Corbon lists their load as 1250 fps with a 165 grain JHP, that's a difference of 10 grains of bullet and only 45 fps between the 40S&W and the 10mm). With the Winchester, at 100 yards, the 10mm is only 19 fps faster than the 40S&W. While I know they aren't the same weight, it was the velocity I was talking about, and therefore, theorhetically, you can hand load 40S&W up to some 10mm velocities, using a smaller grain bullet. Corbon is notorious for loading things very hot, but they are generally still within SAAMI specs, so just going over the spec ever so slightly will get you 10mm velocities from a 40S&W case. Now remember, they also said you couldn't make major with a .355 bullet in a 38 super till TGO did it.

By the way, the first use of the word "Magnum" was used by the French, and it was referring to a larger champagne bottle than normal....

Edited by GrumpyOne
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While I agree with you in theory about the the first part, just because something says "Magnum" on the case, doesn't mean it is one. I mean, if that were the case, wouldn't we be shooting 38 super magnums? :rolleyes: While the .357 is a quite potent round, and you are supposed to use magnum primers, the 38 supers we shoot are even more high pressure than that, and the 9mm major is even more than the super. Even some factory loaded 38 super exceeds .357 pressures. I've been shooting my super with WSP primers almost exclusively, I see no flattening, primer flow etc. (at least to any worrying degree). Do you think that with the lower pressure of the .357 they would flatten and crater and flow with just a small pistol primer? I don't. If that were the case, wouldn't (and shouldn't) you be loading 38 special +P+ with a magnum primer? It is approaching standard .357 velocities, right? But the standard is to use the small pistol primer, not the magnum primer.

To keep from getting too far into the weeds I'll limit what I reply to on this. First off, let's not confuse what USPSA shooters are doing with Super/SC and 9 Major with what the normal intent of the product is. Typically we're pretty well out there on our own so it's not really a reasonable comparison when we talk about a product designed for a specific purpose like small pistol mag primers. The component manufacturers needed something for a handful of cartridges, and they came up with the SPM primer...it's routine use is pretty limited, which is probably why they've been more available than most others lately. The other thing, we don't really know, but I wouldn't be surprised if ammo manufacturers aren't already using SPM for Super+P and +P and +P+ 9mm...they're certainly in the ballpark where they could be helpful.

I'd also suspect that autos and revolvers have slightly different needs when it comes to primers near the limits...and SPM was almost certainly first used for stuff like .357 Mag.

Edit: removed some comparisons that weren't really helpful.

There are some huge cases that don't require magnum primers...like .45 Colt and 44-40...normal large primers work perfectly with them even though you can put a lot more slow powder in them than you can in a .357 Magnum. Even with the extra powder they're working at lower pressures than the .357 is, so they don't need magnum primers.

The second part, well the bigger rounds you are talking about all have a bigger diameter at the primer, and although they may have more powder in the charge, they also have more surface area of powder touching the primer, so you are igniting more powder with the primer in a larger case (even with it being a regular large pistol primer) at the initial time of firing than you would be in a narrower case. Take for instance, Alliants reloading page shows a 158 grn .357 loaded with 8.5 grains of Power Pistol with a velocity of 1,078 FPS, while a 45 GAP shooting a 185 grn GDHP is loaded at 7.8 grains of the same powder, with a velocity of 993 FPS, and a 45 auto loaded with the 185 GDHP and 9.5 grains of of Power Pistol is pushing 1,047 FPS, but it is just a standard large pistol primer. The pressures between the 158 .357 load and the 185 grn 45 auto load would be about the same (heavier bullet, same powder, very close to the same velocity). The .357 has a case volume of 19.5 grains of H2O, while the 45 auto has a volume of 25 grains of H2O. (I probably just made your case, but after reading all this, now I'm confused! :rolleyes: )

If you look at .45acp, the max SAAMI spec pressure is 21,000PSI. Looking at Alliant's printed data for a 158gr JSP with 8gr of Power Pistol they show it at 1,305fps and 33,800PSI. Pretty much any real .357Mag load is going to have pressure way higher than any .45acp load...even +P, which is why you don't need a magnum primer. .45GAP runs max pressures roughly similar to .45acp+P at 23,000PSI, still well below .357Mag.

Keep in mind that primer brisance (how much flame it puts out) isn't easily calculated and that probably makes it more confusing than it could/should be. R,

When it comes to 10mm, I hear you, I was just saying it's possible to get some really hot 10mm loads and stay within pressure limits...to the point that you'd never be able to get with a .40S&W.

Edited by G-ManBart
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While I agree with you in theory about the the first part, just because something says "Magnum" on the case, doesn't mean it is one. I mean, if that were the case, wouldn't we be shooting 38 super magnums? :rolleyes: While the .357 is a quite potent round, and you are supposed to use magnum primers, the 38 supers we shoot are even more high pressure than that, and the 9mm major is even more than the super. Even some factory loaded 38 super exceeds .357 pressures. I've been shooting my super with WSP primers almost exclusively, I see no flattening, primer flow etc. (at least to any worrying degree). Do you think that with the lower pressure of the .357 they would flatten and crater and flow with just a small pistol primer? I don't. If that were the case, wouldn't (and shouldn't) you be loading 38 special +P+ with a magnum primer? It is approaching standard .357 velocities, right? But the standard is to use the small pistol primer, not the magnum primer.

To keep from getting too far into the weeds I'll limit what I reply to on this. First off, let's not confuse what USPSA shooters are doing with Super/SC and 9 Major with what the normal intent of the product is. Typically we're pretty well out there on our own so it's not really a reasonable comparison when we talk about a product designed for a specific purpose like small pistol mag primers. The component manufacturers needed something for a handful of cartridges, and they came up with the SPM primer...it's routine use is pretty limited, which is probably why they've been more available than most others lately. The other thing, we don't really know, but I wouldn't be surprised if ammo manufacturers aren't already using SPM for Super+P and +P and +P+ 9mm...they're certainly in the ballpark where they could be helpful.

I'd also suspect that autos and revolvers have slightly different needs when it comes to primers near the limits...and SPM was almost certainly first used for stuff like .357 Mag.

Edit: removed some comparisons that weren't really helpful.

There are some huge cases that don't require magnum primers...like .45 Colt and 44-40...normal large primers work perfectly with them even though you can put a lot more slow powder in them than you can in a .357 Magnum. Even with the extra powder they're working at lower pressures than the .357 is, so they don't need magnum primers.

The second part, well the bigger rounds you are talking about all have a bigger diameter at the primer, and although they may have more powder in the charge, they also have more surface area of powder touching the primer, so you are igniting more powder with the primer in a larger case (even with it being a regular large pistol primer) at the initial time of firing than you would be in a narrower case. Take for instance, Alliants reloading page shows a 158 grn .357 loaded with 8.5 grains of Power Pistol with a velocity of 1,078 FPS, while a 45 GAP shooting a 185 grn GDHP is loaded at 7.8 grains of the same powder, with a velocity of 993 FPS, and a 45 auto loaded with the 185 GDHP and 9.5 grains of of Power Pistol is pushing 1,047 FPS, but it is just a standard large pistol primer. The pressures between the 158 .357 load and the 185 grn 45 auto load would be about the same (heavier bullet, same powder, very close to the same velocity). The .357 has a case volume of 19.5 grains of H2O, while the 45 auto has a volume of 25 grains of H2O. (I probably just made your case, but after reading all this, now I'm confused! :rolleyes: )

If you look at .45acp, the max SAAMI spec pressure is 21,000PSI. Looking at Alliant's printed data for a 158gr JSP with 8gr of Power Pistol they show it at 1,305fps and 33,800PSI. Pretty much any real .357Mag load is going to have pressure way higher than any .45acp load...even +P, which is why you don't need a magnum primer. .45GAP runs max pressures roughly similar to .45acp+P at 23,000PSI, still well below .357Mag.

Keep in mind that primer brisance (how much flame it puts out) isn't easily calculated and that probably makes it more confusing than it could/should be. R,

When it comes to 10mm, I hear you, I was just saying it's possible to get some really hot 10mm loads and stay within pressure limits...to the point that you'd never be able to get with a .40S&W.

All I was really trying to say was that if a 9mm Luger has a max pressure of 35,000 PSI, a 40 S&W has a max pressure of 35,000 PSI, and the 357 magnum has a max pressure of 35,000 PSI, then the only difference (pressure being pressure) in the loads would be the magnum primer. If that were gonna be the only difference, since the max pressures are all the same, then logically the only reason for a magnum primer is to ignite a larger charge of powder, and therefore wouldn't have any effect on any pressure signs. If it were a pressure thing, then the 9mm and 40 would also have the same percieved issues with primer flow, cratering, etc., because almost all factory ammo in these calibers (correct me if I'm wrong), are loaded with regular small pistol primers.

I realize I was wrong in trying to compare the 45 to the .357....But let's compare the .357 SIG to the .357 magnum. The 357 SIG is rated at 40,000 PSI, but still a regular small pistol primer. It's 5,000 PSI higher than the magnum, yet the manufacturers see no reason to build it with a magnum primer......Maybe not because of the pressure, but because of less powder to ignite.....

As far as the 10mm goes, you are correct. There are some really hot loads out there, but again, all things being equal, the hottest 40 factory round is gonna compare somewhat to a slightly lower 10mm factory round...So, it wouldn't take much to equal the two up, at least to the lower end ( maybe even the mid range, but that might be pushing it!) of the 10mm spectrum.

Here is a very good article from the Shooting Times by someone who worked at CCI primer division.

http://www.shootingtimes.com/ammunition/ST_mamotaip_200909/index.html

This is taken from that page:

Magnum Primers: Use As Directed

Most primer makers offer a standard and a Magnum primer in each size and application. The Magnum primer offers more power for challenging ignition scenarios. A large-capacity case, a heavily deterred propellant, or extremely cold weather (less than 20 degrees Fahrenheit) typically makes the Magnum primer desirable.

There are two ways to make a Magnum primer—either use more of the standard chemical mix to provide a longer-burning flame or change the mix to one with more aggressive burn characteristics. Prior to 1989, CCI used the first option in Magnum Rifle primers. After that, we switched to a mix optimized for spherical propellants that produced a 24-percent increase in flame temperature and a 16-percent boost in gas volume.

Literature from some propellant manufactures often says that their products do not require Magnum primers. This is perceived as a good thing because Magnum primers are made in smaller quantities and require more chemicals; therefore, they are more expensive. However, I had to take a different view, one based on real-world issues.

We tested loads at both maximum normal pressures and at the starting loads (some labs calculate start loads—we shot them). Standard primers caused no ignition issues at the max load but posted higher extreme variations in pressure and velocity in the lower pressure regimes of the start loads. In extreme cases, the start loads produced short delayed firings—probably in the range of 20 to 40 milliseconds but detectible to an experienced ballistician. Switching that propellant to a Magnum primer smoothed out the performance across the useful range of charge weights and completely eliminated the delays.

If I’ve recommended a Magnum primer in reloading data I’ve developed, it’s because my lab results show it’s needed.

Further down in the article, he explains why everyone thinks CCI primers are harder than others....

Edited by GrumpyOne
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  • 2 weeks later...
Standard primers caused no ignition issues at the max load but posted higher extreme variations in pressure and velocity in the lower pressure regimes of the start loads. In extreme cases, the start loads produced short delayed firings—probably in the range of 20 to 40 milliseconds but detectible to an experienced ballistician. Switching that propellant to a Magnum primer smoothed out the performance across the useful range of charge weights and completely eliminated the delays.

Interesting. Possibly explains why my SD dropped to 6 when I switched from Federal SPs to Federal SPMs in my 9mm 147/N320 loads.

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