357 Mag primers

ECM4

New member
Just picked up a .357 mag. Going to start reloading for it soon. I plan on using Missouri Bullet 158 gr. SWC. I’m wanting to use Win 231 since I buy it in bulk and use it for every pistol I currently reload for. The load data I have for this says use magnum primers. With Win 231 I can use a regular small pistol primer correct? If I use regular primers and not magnum will it change the load data at all. Starting load says 3.4 and max 5.0. I’m just using these for light target loads for plinking.
 
Yes, standard primers work just fine with W231. In my .357 tests, I loaded 5.0g (926fps) to 6.0g (1072fps) of W231 under 158g SWC. Used CCI-500s. 6 1/2" barrelled Ruger BH used for testing.
 
Use magnum primers according to the powder being used, not the cartridge designation. Typically, magnum primers for the .357 Magnum are used with HS-6/W540, H110/W296, and I use them with IMR4227, although others don't.

Don
 
What USSR said.

For clarity, W231 doesn't need a magnum primer. I've never seen published load data that states so. If it exists (and I'm not disputing the notion), I would disregard it.

I love W231. And I load a lot of 357 Magnum. But I have never had much luck with the combination. I find W231 to be really spunky in the 357 Mag and so it makes me nervy. Like night n day compared to how it behaves (excellent!) in 38 Special. Go figure.

I remember many years back I tried a starting load per the Speer Manual for 125 JHP's (if memory serves). At the starting load, I had very difficult extractions and flattened primers. I figured I erred in my loading process. So I produced another batch with the same result.

That, and the fact that you're loading lead (and heavy ones at that), I would advise a propellant that is a touch slower. Straight lead slugs like a more mild pressure curve. Unique (which I don't actually like) is a great choice in this situation. HS-6 too (which would use a magnum primer). Either one is going to run sooty (because you won't be running them to high pressure), but they will likely mitigate leading - a more than fair trade-off.

MoBuCo makes good bullets. You'll be pleased with their 158 SWC's.
 
Definitely no need for mag primers with 231, but I would agree with Nick_C_S that it is not the best powder for the application. Hodgdon Universal works pretty fair and is cleaner than Unique. Also note; avoid Remington 1 1/2 Small pistol primers with .357, they cannot sustain the pressure of the round.
 
I used a lot of 231 powder in a .357mag, but for very light target loads only. When I was shooting the speed/precision portion of a three man team shoot I used that powder with cast bullets and got great accuracy. However, I've never found it to be a good "mag" level powder. I think for light plinking loads you'll be happy with it. And no, you do not need mag primers with this powder.
 
I prefer to use magnum primers with the very slow powders when advised just for the sake of best practice, but my understanding is that both will work and the reason to use one over the other is to minimize extreme spreads in velocity from inconsistent ignition. It seems some powder is more consistent with one type of primer or the other depending on load and powder characteristics in a given cartridge.

If you don't really care about ES in a handgun then it's not a big deal to use whatever is handy.
 
In the case of most published data, the source chooses one specific primer for development testing of all powders used in a given cartridge. Hornady (#9), Nosler (#8), Sierra (V), Hodgdon, Western, and Lyman (#49), all specified magnum primers in all of their published loads regardless of the powder used. On the flip side, Alliant specifies regular primers in all of their recently published 357 Mag loads.

For many years, Speer has specified a combination of regular and magnum primers in their published data. They specify magnum primers in many of the loads that utilize slower and/or ball type powders, and standard primers for the rest.

One reason reloading component manufacturers tend to specify magnum primers is due to the belief that most reloaders will tend to use "magnum" primers for their "magnum" loads used in their "magnum" handguns.

Another reason magnum primers are specified is related to their performance. In many instances a magnum primer (versus a standard primer) will produce higher operating pressure for a given load. So specifying magnum primers offers a bit of cushion in the case of primer substitutions. If the opposite approach were to be taken (specifying standard primers), higher than intended pressures could result if magnum primers are substituted.

A third reason magnum primers are specified is powder based. Some powders can be harder to ignite and a stronger (magnum) primer can produce more consistent results when those powders are used.

Ed Matunas, who loaded and tested more ammo than most of us ever will, said regular primers give the best results in the 357 Mag when powder charges are 10 grains or less. (The context of this statement was an article stressing accuracy over maximum velocity).
 
When I first started experimenting with 357 mag. with 125g bullets, Extreme Preprimed brass, H110 with a starting load of powder and a light crimp, I ran into a nitemare,, half my rounds turned into squib loads, with unburnt powder and me looking like an idiot on the range pounding out bullets from my nice ruger sp100. I called Extreme to ask if they put magnum primers in their preprimed brass, and the lady actually asked what are magnum primers!!, I just said never mind and now I just use that preprimed brass with the faster powders with no problems, my lesson learned, be careful using unknown components and H110 likes a heavy load,and a good crimp, I also only stick with 158g hardcast bullets now with H110.
 
My approach is to try both. The one that produces the lowest velocity SD gets the nod, and I just adjust the powder charge, if necessary, to give best accuracy with that primer. Usually, it makes less difference than people suppose, but every once in a while you run into a gun that likes one a lot more than the other, and I've seen it go both ways.
 
I am unaware of the failure of proper loads of H110/296 to be ignited by standard primers. What ballisticians will tell you is you find variation in the delay between the primer strike and pressure unseating the bullet if the primer is too weak to produce consistent ignition. The normal delay is around 2 ms. Allan Jones commented that bad primer mixes he'd experimented with could run 10 times that. The bottom line is these delays are like extending lock time: you give the muzzle more opportunity to move before the bullet gets out.

On the other hand, I've seen examples of over-strong primers unseating bullets during that 2 ms or so normal ignition delay. The .22 Hornet is famous for having this problem and producing irregular velocities when it is happening. If you see groups open up using the stronger primer, particularly in a small capacity case, that is a possible cause.

Velocity SD will tell you if the ignition is consistent. Group size will tell you if you are dealing with too much ignition delay for your gun or hold. Again, other than testing different primers, I don't know of a way to guarantee what you are doing is squeezing the most best out of a load or not.
 
"...can use a regular small pistol primer correct?..." Yep. The use of magnum primers is about the powder, not the cartridge name.
For some daft reason, Hodgdon says use a magnum primer for magnum named cartridges, but not for other cartridges using the same powder. Look at .357 data and .38 Special using Win 231 data. They do the same thing with H110 in .357 and .30 Carbine. And with IMR4227.
 
The reason is simple. They choose one case and one primer and one test barrel length for all the loads recommended for a particular chambering. It's the only way the powders can be compared on an apples-to-apples basis.
 
I have to think that the advice to use magnum primers in all magnun cartridges is a marketing tactic.

I'll give an example.

For 40 years, I used ********* spp in ALL small pistol loads with complete satisfaction and safety. Tha's hundreds of thousands of rounds without a primer failure.

A few years back ********* started printing a warning on the spp boxes not to use them in magnums or the .40 S&W.

I posted my experience with these primers, and the mods here deleted my post and warned me rather sternly to never post advice that contradicted a manufacturers warnings. That's why I didn't post the brand name here.

I've chronographed my recent loads with these primers and compared them to ammo loaded 30 years ago. Same velocity. No difference.

I can't help but believe this warning was meant to help sell their magnum primers.
 
I, like Unclenick, sometimes will do back to back primer tests with a given load and check them over the chronograph. The ES will tell the tale. I started to do this when we had the 'primer' crisis and wanted to see what worked. For most powders, I found I could use CCI normal, CCI magnum and Winchester interchangeably. Winchester I found was between the two in 'hotness'. Hotness defined as an increase in velocity and yes there is a difference. On the other hand sometimes it was obvious that one worked better than the other. Now I don't load 'hot' loads, so not working at the 'extreme' high edge, therefore not to worried about over pressure. So it pays to test both if looking for 'best' possible load. I found 2400 to work best with standard primer for example in one caliber ES was Magnum 115fps and standard 54fps. My tests were always with 15 rounds per load to get best possible results. As with above I won't list loads. Something you have to work out for yourself....
 
While magnum primers are not needed for W231/HP38, if a published recipe calls for them, it is deemed safe. Some manuals use magnum primers for all the powders listed due to simplicity....just like some reloaders do. Winchester only makes one primer for Large Pistol and it's suitable for both magnum and standard applications. So if your recipe calls for a magnum primer and that's what you have, go for it. If the recipe uses magnum primers and the powder itself does not need them, and you have standard primers go for it. The exception is basically a few slow burning powders like H110/W296 that need those primers for consistent ignition, and this is especially true is small cases like .357.

You will find as you gain experience that some primers may give more or less accuracy in your firearm with certain projectiles and certain powders. This is what handloading is about. Some folks will tell you to never use magnum primers with 2400, while some published recipes show them being used together. Stick to manuals and you will be safe until you gain enough experience otherwise. Only use info gleaned from gun forums that can be verified by manuals or is stated to be true by a good majority.
 
Load data appears to often list primer spec by cartridge rather than the powder to be detonated. I wouldn't worry about what the data says except for H110/W296. I also have adopted the trick of using magnum primers on powders/loads that leave unburned granules. The magnum primer supposedly has a longer burn.

Use of powders that burn faster than magnum powders should be limited to mid range, or the recoil impulse could be sharper than with a real magnum load. I recommend AA#7 if you are going to eventually load toward a real magnum round. It is interesting to shoot but not crazy.
 
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