Primer Alternatives for 357 Magnum

DMW1116 said:

I recently made an impulse buy of an antique 357 Magnum Blackhawk so I did not plan my ammo situation. I have small pistol and small rifle primers, but there are no small pistol magnum primers to be found. Can I substitute either of the others? Some of the loads I want to try are pretty tame so I figure the small pistol is pretty safe, squibs aside.

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It depends on the powder(s) that you use. Look up the powder makers website for data to see what they recommend as primers in their data.

For less than full power loads standard small pistol are fine, if not best. Generally, magnum primers are only necessary with certain slow pistol powders where maximum power is desired and magnum primers are specified. For instance, W296/H110 powder loads usually specify magnum primers.

If you stick with fast-to-medium burn powders - in the Bullseye, Red Dot, W231, AA#2/5 through AA#7, Unique and 2400 powders range - SPP are typically recommended over SPM anyway. It’s when you venture into the Lil’Gun, H110/W296 loads that SPM becomes the norm. I won’t recommend using SRP with those powders. Not even in a rifle.

In this Speer link, in 357 magnum, H110/W296, Lil' Gun, HS-6, and sometimes #9, they list CCI 550. Most others they CCI 500.

If you're pushing to max load, I'd avoid Rem 1 1/2, as they state to avoid using in higher pressures pistol cartridges.

I did the same thing and got into 38/357 a little over a year ago on a whim. Brass bullets and powder were pretty easy to find. I could find no spp but have plenty of srps. They function fine in my .357 and 38 loads. I run Bullseye in the 38 and H110 in the .357 with good accuracy and no issues. I do not run max loads in either one. Primers and brass look normal after firing as well. ymmv good luck

I loaded up an odd ball load of 158gr cast with a medium load of HS-6 and Small Rifle Magnum primers. I put about 20 rounds through two different revolvers and they shot fine.

This topic comes up fairly often of late due to the primer situation, or rather lack of it. I have basiclly shifted to using SRP for all my loads to simplify inventory and ordering. All my loads are worked up using SRP and I find no measurable difference in results. This was before I purchased my first crony so I did not compare velocity to SPP but recoil and accuracy were the same. The only problem I had were some of my stryker fired pistols would not reliably fire the SRP so I still use SPP for them as needed. I find as long as you work up your loads it is safe to do so with SRP.

Sadly, I can't provide the link right now - but somewhere on this forum I read a thread where someone with a pressure sensor actually ran every available small primer (type) through some pistol cartridges. (9mm and 357 I think??) Tested 3 or 4 combinations of powder and various primers.

IIRC, The end result was that with the faster powders and loads that get fairly complete burn ratios - there was no practical difference between regular, magnum, rifle, and rifle mag primers for some loads. The pressure curve was already maxed out due to the complete burn.

Slower powders exhibited some variation but I believe the results showed there that a safe load,remained a safe load - within the expected limitations.

If you want Original Magnum Power, No 2400 does not require magnum primers.

If you have 296 or other Ball powder, small rifle primers are fine.
Before Federal made magnum primers, they recommended their small rifle primer for .357 so it is not like you would be doing anything that had not been done before.

I’ve never used anything but spp in my 357. That said, I also have never used 296. I do use a lot of 4227 and 2400.

I intend to run this test over a crono with 4227. This powder is very hard to get a good burn and it works great in a 308 with a lrp. There is a few accuracy articles discussing using the least powerful primer to smooth out the combustion cycle. This results in things like srp 308 cases, and observations of no major change in 45acp when using spp. Will they all work yes, are they all safe yes if worked up. Are all equal and just as good for accuracy, testing is required.

I also concur with what others have said above. That is, for fast burning powders, a SPP will work fine in a 357 case with recommended 357 charges. I use SPPs frequently with charges of 700-X (a fast burning pistol powder) in 357 cases. Never an issue with 100 % ignition reliability in all of my revolvers.

From reading and researching, it is also my understanding that a major difference in SRPs and SP mag primers is the thickness of the cup itself rather than a difference in the primer compound used between them. I've read that SRPs have a slightly thicker cup to accommodate higher chamber pressures in a rifle. That is the reason, I've read, that some pistols will not reliably ignite SRPs on a consistent basis.

That is also the reason why SP mag primers are not indicated/recommended for use in small rifles with rifle charges. The risk being, of course, pierced SP mag cups resulting from pressures exceeding their capability when used in a small rifle.

Bayou52

Walkalong did some primer testing that was pretty interesting. I never can find his post though....

Hartkopf said:

Walkalong did some primer testing that was pretty interesting. I never can find his post though....

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This?https://www.thehighroad.org/index.php?threads/9mm-primer-test.840256/#post-10902641

Post #66

Similar trial, I saw no difference in velocity between primers with HP38 in 9mm, except that RP 1 1/2 were a smidgen faster than any other, including magnum and rifle.

I later found that CCI BR4, the target rifle primer I bought for my good AR, is a hard primer and had to be hand seated very firmly for reliable ignition in a pistol.

If you have Alliant powders, take a look at their recipes for .357 many (most? all?) call for regular small pistol primers:

https://www.alliantpowder.com/reloaders/

kcofohio said:

This?https://www.thehighroad.org/index.php?threads/9mm-primer-test.840256/#post-10902641

Post #66

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Yes post 66. ES and SD tightened up with the rifle primers. Reason enough to use SRPs as long as the gun will ignite them. EDIT: AND NOT BLOW UP IN YOUR FACE

In my experience, I could not measure a difference (target, velocity, or velSD) between CCI SPM and S&B SP (non-mag) under a full house load of H110, 158gr bullet. Warm weather, good hard crimp.

It did make a difference with HS-7.

I keep this article bookmarked for just such conversations:
https://www.shootingtimes.com/editorial/ammunition_st_mamotaip_200909/100079
[periodical] Shooting Times, "Mysteries And Misconceptions Of The All-Important Primer;" Allan Jones; January 04, 2011

from the Shooting Times article:
"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."

There's more to it and it's about the best summary read you'll find from a genuine expert on the subject in any publication. Internet lore and forum posts aside, a lot of us DO things we'd never recommend; and some folks even recommend things they'd never actually do. I know small rifle and small pistol primers are almost interchangeable, under a very limited set of circumstances, but I won't recommend it because I don't have and can't find legitimate, tested and published loading data that says small rifle and small pistol primers should be interchanged and the circumstances where it's recommended.

also see: "A primer on primers: rifle and handgun primers start everything going.." The Free Library. 2009 Publishers' Development Corporation 19 Oct. 2021

DMW1116 said:

I plan to use Alliant 2400 as I already have some for 357 power loads from a 30-30. I have not looked at their load data yet. I’ve only looked in my Lyman manuals for 2400 loads.

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You can find loading data going back to the 1930's for 2400. Some of the older data is for bullets you won't find in more modern sources because the big names don't make them anymore, or "better" designs came out; but, those bullets are still available as molds, if you decide to make your own, those older sources can come in handy. Just be careful with older data for all the usual reasons. And don't go drinking out of any water hoses, wear a mask in public AND private, don't kiss no easy women (or men) and always look both ways crossing the street. (yes, it is a wonder we survived before the nanny-staters took over)

DMW1116 said:

I plan to use Alliant 2400 as I already have some for 357 power loads from a 30-30. I have not looked at their load data yet. I’ve only looked in my Lyman manuals for 2400 loads.

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One of the big companies - Speer, I think - actually recommended against the use of magnum primers with 2400, at least at one point in time.

I personally do not use magnum primers in the .357 unless loading with H110. I much prefer 2400 in the .357 and have fired many thousands of rounds with 13 grains behind 158 SWCs and lit with Federal SPP.

kcofohio said:

In this Speer link, in 357 magnum, H110/W296, Lil' Gun, HS-6, and sometimes #9, they list CCI 550. Most others they CCI 500.

If you're pushing to max load, I'd avoid Rem 1 1/2, as they state to avoid using in higher pressures pistol cartridges.

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Silly me, I forgot the link.
https://www.speer.com/reloading/handgun-data.html

AA#9 or 2400 use small pistol primers. No Magnum primers required..enjoy..


Thewelshm