I have never used Small Pistol Magnum Primers in my 357 Magnum 158 grain .358" diameter L-SWC loads over 6.0 grains of Unique. Does anyone recommend the magnum primers for this load?

I would save the magnums for other loads. I doubt you would be over pressure with the magnums since the listed velocity is only 1kfps but obviously you should reduce and work back up when switching components. If that's all you have go for it. Otherwise it's a waste.

The magnum primers are for hard(er) to ignite powders than Unique. The cups may also have slightly different specs to better withstand high pressures. In 50 odd years of reloading .38/.357 I've only used the magnum primers once, and that was recently, because the load data was developed using them AND, I'd bought 500 of them by mistake.

Unique works just fine with both magnum and non-magnum primers.

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213th FBINA

Thanks for the replies. I'll stick with Small Pistol Primers.

Most handloading manuals specify magnum primers with all.357 loads due to the tall case and air space with light loads. My chronographing tests show improved consistency with magnum primers with all .357 loads, light to heavy so that’s all I use.

I use SPMP with 2400, SPP with Unique, never problems since 75.

You could use magnums in it, but there's no logical reason to support it outside availability.

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it just needs more voltage

If you get a pierced primer, ever, switch to magnum.

If using 2400 powder, a WSPM primer will require a reduction in 2400 powder.SAAMI PRIMERS | The High Road

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I have often read that the Magnum primers were for slower powders like H110 or 4227.

I have noticed myself that a magnum primer can clean up a dirty load (unburnt grains of powder) some as well.

Prescut

Alliant doesn't recommend magnum primers with Unique in the .357 Magnum. I'd rely on their expertise.

Small Rifle primers will work just as well. Pretty much identical to a SPM primer. I have used SR primers only in all of my .38 Special and .357 loads for many years, and even in several other calibers.

I have used Federal magnum SPP exclusively in every 9mm, 38, 357 that I’ve loaded for the last 5-6 years with Titegroup, Bullseye, Unique, Universal, CFE Pistol, 2400, H110 and Lil Gun. I have seen no noticeable difference except it does help some powders burn cleaner. I’ve checked loads as light as 2.7gr Bullseye to Max loads with 2400 with a chronograph and saw more difference from gun to gun than I did from Std to Magnum primers. No high pressure signs. Your results may vary but I’ll continue to use magnum since that’s all I have

Magnum primers are only needed for powders which are hard to ignite like W296/H110, HS-7, HS-6 and the like. They work better when lit by a magnum primer.

Unfortunately load manuals these days use SPP for .38 Special and other "standard" cartridges while they use SPM primers for anything that has a "magnum" name. I wrote Hodgdon and asked them why and they said they use and list a magnum primer for cartridges like the .357 Magnum because even if the powder doesn't need one because they are concerned some reloaders will not read the primer used and assume a magnum primer is required. That may raise the pressures making the max powder charge no longer within the max pressure limits.

If you have older manuals like the Speer 8 or 9 look at the data for the .38 Special using HS-6/W540 and you will see a magnum primer was used in the load development.

Unique and 2400 are very old powders developed before magnum primer were made. They seem to perform better with a standard primer over a magnum primer. The SD and ES numbers are lower with standard primers so that's what I would use, even with 2400 in the .357 Magnum.

I hope this helps a bit...

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SWCA #3437

The older genuine Alliant and Hercules manuals used Federal 200 primers with all loads and powders, even Bullseye and Red dot. The current published Alliant data isn’t the data originally developed by them.

I gave up on pistol pistol primers, standard or mag, for my full .357 "magnum" loads years ago and only use Federal 200 Small Rifle.

No. No need for mag primers with Unique.

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Grumpy Old Man With a Gun

That’s correct

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213th FBINA

Magnum small pistol primers aren't just about explosive material quantity. The most important aspect is primer cup thickness. I would recommend loading .357 magnum loads with magnum primers for the thicker cup...primers are the main weakness of small-primer handgun cartridges because even the magnum versions have thin cups. In fact, if your hammer system can handle it I'd recommend working all loads up using small magnum RIFLE primers to get the super-thick cups that don't flatten out like velum at 36K psi.

Literally ALL reload manuals say to use small pistol magnum primers. I only use them and I've been successful with hot loads H110 Hornady XTP 125 and 158 grains projectiles.
You're free to use what you want, but I have a 100% success and still have all my fingers, I'll stick with that.

Most of the primers I have purchased in the past 2 years, have been magnum primers, because those were the ones not being purchased by others. 1K of large rifle magnum, and 1 k of small pistol magnum. Small pistol magnums can be easily made to work in small pistol or small rifle brass.

I've loaded 357/44 mag for years, NEVER bought a mag primer in my life. I use 2400 exclusively, but standard primers worked 100% with 110 and 296 as well.

Right now, you use whatever type of primers you can find. Not a good time to be choosy.

I'm happy to hear you have had no problems with W296/H110 with standard primers but when used with Magnum primers the powder burns more completely and the ES and SD numbers drop in most cases.

Slow hard to ignite powders like W296/H110, W540/HS-6, W571/HS-7 ( both HS-7 and W571 are now discontinued) and other powders like them shoot better when set off with magnum primers.

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SWCA #3437

Negative.

My Speer manual lists small pistol primers for most loads. They list magnum primers for loads using certain powders (W296, HS-6, HS-7, etc.)

edited to add: I was concerned about the age of my Speer manual (12th edition, 1995). Their online data still has magnum and standard primers based on powder.

additional edit: I removed mention of a different manual as there was no mention of Mag primers for any loads using small pistol primers leaving things ambiguous.

Don’t own a chronograph do you? If you did you would see how extremely poor your handloads with 110/296 and standard primers actually are.

Remington primers- https://www.ssusa.org/content/reming...istol-primers/


"Indeed, Remington’s ballistics tables list the recommended primers for each caliber that Remington loads, handgun and rifle. The 1½ primers are listed for the 25 Auto, .32 S&W, .32 S&W Long, .32 Auto, .380 Auto, .38 S&W, .38 Short Colt and .38 Special. None of these cartridges exceed 25,000 psi peak chamber pressure limits. Surprisingly, the 1½ primer is also listed for the 9mm Luger, the 9mm +P and .38 Super. These latter calibers are not low pressure. The 9mm Luger has a SAAMI (Sporting Arms and Ammunition Manufacturers’ Institute) pressure limit of 35,000 psi, and the +P version’s limit is 38,500 psi. The .38 Super has a SAAMI pressure limit of 36,500 psi. These compare with the .357 Magnum and .40 S&W pressure limit of 35,000 psi, and the .357 SIG’s limit of 40,000 psi. If the 1½ primer is not appropriate for the .357 Magnum and .40 S&W, how can it be appropriate for the 9mm, 9mm +P and .38 Super, which have the same—or even higher pressure limits?

This has caused confusion among some reloaders, myself included. In fact, I was unaware of this warning when I first bought 1½ primers and used them in 9mm Luger loads. I thought the 1½ primers were “standard” primers, and the 5½ primers were “magnum” primers, since that is how they are listed in many primer charts."

In my 686 I have been loading sub 1000 fps target loads with True Blue and, due to availability, have been using small pistol, small pistol magnum, and small rifle primers without any problems. No signs of any pressure issues and if there is any affect on accuracy, it's too small for me to notice.

I have been using SRP in all of my handgun loads this year because of the paucity of SPP. I’ve had zero issues, firing in Glocks and my cheapie Beretta APX, due to the thicker cups. All of my reloads are mild pressure-wise so no concern with using small rifle primers. As others have stated, I am reasonably sure that SRP = SPM.

This is an epiphany I have had recently. I have heard the argument for the thicker primer for the higher pressures, but as you stated, 9mm and 40 both run pressures the same or higher than 357 mag, but I have never seen any load data call for mag primers in either, so that debunks that argument.

Only argument I have heard that does make sense is that some powders need a hotter flame to burn consistently. And that some ball powders such as H110 may burn fine at normal temps, but in cold weather environments, that is when you really start to have hang fires and the like and a mag primer will take care of that.

Other conclusion I have come to. Magnum in a cartridge title is used in a different context than Magnum in a primer name. 2 different uses of the term. In a cartridge, it was really just a marketing name to sell products. In the primer, it really means a hotter flame and also varies from manufacturer to manufacturer.

For example, a .270 Winchester runs higher pressures than a 7mm Rem Mag. And as you stated, the 9mm and 40 may run higher pressures than a 357 mag and 44 mag.

Rosewood

The powder and to some extent the amount of that powder determines when a magnum primer is used .
Ball powder and large charges of slow burning powder like 2400 and H110 can benifit from magnum primers .

Unique is a medium burning , easily ignited powder .
6.0 grains is not a large amount ... no magnum primer needed ... BUT ...
If all you have are magnum primers ... in this load you could use a magnum primer and get a few extra feet per second in velocity .
It will not create dangerous pressure in a 6.0 grs. Unique load ( a max. load like 7.0 grs would call for a reduction but 6.0 grs. is fine) ... you might even get a bit better accuracy in the 357. magnum case .
Load up a few and test them ... the primer shortage is causing a lot of folks to start using magnum primers because that's all they have left and/or all they can get !
Gary

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Lately I've found mag primers are more readily available & priced cheaper than std . Large rifle all I've seen are CCI 34's & Ginex .

Regardless of whether you are loading with Unique or other powders, use what primers you have or what you can find. Your gun, your components, and your shooting skill are different from those of others.

I've seen slightly better accuracy with a magnum primer, #2400 powder, and a 160 gr. SWC cast from an H&G #51 mould and fired in a 6" Python vs. the same with a standard primer. Hardly definitive proof of anything.

Try both primers (or as many varieties as you can find) and fire some ten-shot groups benchrested at 25 yards. A chronograph would be handy, but not necessary. If you use a chronograph, look at the velocity figures and check the target for group size; don't fixate on SD and ES numbers which are very secondary.

I’ve tried spm and srp in 800-950fps unique,win244, and aa5 loads in 357 brass, 158gr plated and jacketed rn and swc, they do burn cleaner than sp in my experience.

2400,h110, and 4227, I started at the minimum, I found the accuracy I was after with the charges lower down the spectrum vs what sp achieved, not every gun is the same obviously, but you get the idea. 2400 and 4227 were rancid filthy with regular sp’s, h110 wasn’t nearly as bad as those two.

Like I said above, the need for a magnum primer is powder driven, not by the word Magnum in the cartridge. IMO Unique and 2400 don't require a magnum primer. They are very old powders which were formulated well before magnum primers were ever thought of. Hard to ignite ball powder are the magnum primer candidates.

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SWCA #3437

I have been trying 6g Unique with both hard mix and reclaimed range lead 158g LSWC gas check, sized .357, (what I got), with both standard and Magnum primers, in 357 case. Accuracy is shotgun cylinder choke. In a 586 4" same bullet over 4.1g 231 in 38 spcl case with std primer is more near one hole at 10 yds.

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"Don't Give Up the Ship"

These days I'll use what I can get my hands on... I'm currently using Small Rifle Magnum primers for 357 loads and it works fine.

I've found very little difference. Either one would be fine, especially with a light load like that.

Magnum primers seem to give maybe 10-15 more fps at the muzzle on my chronograph, so they may be just a touch hotter.

But people always say that 296 or H110 need magnums, and I've found that this is not the case.

Winchester even used to make primers that were marked as either mag or standard. I don't think there's much difference.

I've not found this to be the case. I get good performance out of either standard or mag primers in heavy loads with H110 and 296.

And in the 22 Hornet with either of those powders or Lil Gun, I guess noticeably better SD's with standard small pistol primers over small rifle primers.

The Hornet generates a decent amount of pressure and the SP primers don't get cratered or flattened at all.

The reality is that you need to base the primer on the ignition requirements of the powder in a particular cartridge case, rather than making blanket assumptions about “magnum” cartridges or powders.

For Unique, a magnum primer isn’t required, ven in a large case In a large case a primer with more brisance just scatters the powder more before it ignites and that can create pressure spikes. I use Unique in large cases like the .38-55 and .45-70 and use a square of 1/4” quit batting to reduce volume, but it’s still a lot larger than a .357 Magnum case. Small primers work fine.


Even with a slow burning power like 4227 in a small case, like the .22 Hornet, using a magnum primer is both not necessary and can boost pressures significantly - on the order of a 75 fps increase.

——

Based on 36 years of handloading in a very wide range of cartridges including a few where data isn’t available, less primer “brisance” is better, until it’s not in most pistol cartridges and smaller magnum cartridges.

Then if you see a wider standard deviation in the load, step down a bit on the powder charge, work back up with a magnum primer and see if the SD is better.

Some time back there was an extensive thread on the differences between primers that went into great detail on the qualities of the cup. IIRC, there wasn't any significant difference in thickness either between or within brands. However, there wasn't any information on the ductility of the metal. That is, how easily it deforms, which could make a difference in both sensitivity and deformation under pressure.

Between the excellent and informed experience of many here, coupled with published Lyman Reloading data, I continue to use CCI550 magnum primers in all my 357 Magnum loads, mid range to magnum…”start low, work up…” and use a chronograph to keep yourself honest!

I finally have the space (Nevada, 85%+ is public land!, BIG state) and freedom to use a chronograph, back when living in the Northeast, indoor and outdoor ranges precluded their use…

It's very rare for a flake powder to need a magnum primer. 2400 in magnum loads comes to mind so far as getting recommendations for a mag primer, but just about as many will say it's not needed. With spherical and ball powders, it's often a matter of the bullet and the amount of powder used to obtain a specific velocity goal.

Magnum primers for everything that isn't flake or disk. Unique is a disk shaped powder so no, it doesn't need a mag primer.



W-296 and H-110 is flattened ball so use a mag primer.

2400 is cylinder shaped so use a mag primer.

I'm loading up some 357 this week with 2400. I don't have any mag primers but I wish I did.

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That's just somebody talkin.

I just got 2 more pounds of Unique. I also have 2400 that I can load 357 with... And a 1000 Fed SPM primers... I also have plenty 296

I started handloading with flake powders and .41 Magnum in 1986. Years ago, the first reports of lot variations with Blue Dot surfaced. I started using spherical or ball powders closest in burn rate: No 7 & No 9 for example. I've rarely revisited flake powders. One reason being that sphericals with the lowest bulk densities, are still denser than flakes. And since powder measures work on the principle of gravity? Another reason being excessive flash. Blue Dot and Power Pistol, and testing loads at night are pretty impressive if flamethrowers are your thing.
I was also aware that some well known writers sometimes reported getting better results using standard primers for max charges of W296/H110. And for those who are not aware, Accurate 11FS is another variant of the original 296, but with a flash suppressant added. Works pretty effectively, though a bit slow burning for even a 4" combat magnum.
I have really grown to like Ramshot Enforcer/AA 4100 made by Clermont in Belgium. Those people really know how to make great powders. In the case of .357 Mag, I've found that loads could be improved by using a standard vs magnum primer. It is slightly faster burning than W296, but misrepresented on several burn rate charts as being closer to AA No 9 than it is. That is not the case as can be determined by chargeweights in handload data.

I should also mention that all standard primers are not created equal. WSPs tend to be a little warmer than CCI500s. My experiences with Federal SPMs has not been good. Maybe age or some other factor. WSPMs should light up W296 very easily. If you have standard primers, you might want to try both for 2400. I recently got a hold of some Ginex that I'll be testing soon. Appear to be clones of CCIs and made in Bosnia-Herzegovina. We'll see.

I use small rifle magnum primers with N110 in 357. Works great!

Read linked page to the bottom. https://www.ssusa.org/content/reming...istol-primers/

CCI 400 Rifle primes are about the same. As pressure goes up, primers flow. Just like Rem 1 1/2. Or 6 1/2.

GOOGLE- "Mysteries And Misconceptions Of The All-Important Primer"