357 Magnum Loads

[Marshall 357]

Do I need to use magnum primer for 357 magnum loads? What is a good target load?

[Vulcan Bob]

It all depends on the powder being used. Ball powder such as WW 296 and slow powders like H-110 do need a magnum primer. Best bet is to follow the recomendations found in a modren reloading manual.

[Snapping Twig]

Magnum refers to velocity more than anything else, so the components aren't as important in and of themselves.

Magnum is @ 1000 + fps, give or take.

Magnum primers are a personal choice based on powder type and pressures, so you'll have to get a few books and compare the data.

Just to highlight how hard and fast the rules are, I don't use magnum primers to light off my H110/W296 magnums and I have zero issues with unburned powder, etc. I use WSP.

A good target load is...

Using a magnum case, 5g W231 under a cast or jacketed 160g bullet. A little more than a Special, light for a magnum.

[duckloads]

I shoot 158gr lead SWC with Unique and standard primers. I forgot the powder charge. They are accurate enough for an indoor range.

For now, My favorite is a 158 gr JFP from speer with H-110 and magnum primer. I'ts a full magnum and plenty accurate to 50 yds out of my 686 w/ 8-3/8 barrel.

[buck460XVR]

Originally Posted by Marshall 357

Do I need to use magnum primer for 357 magnum loads? What is a good target load?

This info and much more can be found in any legitimate reloading manual. Good manuals are as important as any other reloading component and attempting to reload without them is just asking for trouble.

[bronco45]

Magnum pistol primers will give you a 10-15% increase in pressure in your loads. I only use them when recommended in the manuals and at the powder charges the manual recommends.

[michael thornton]

for just plinker loads in 357 i use 158 cast swc over 6.0 grains ok unique, for my hot loads with 158 jhp i use 2400, i use std primers with both loads. mike

[ArchAngelCD]

1. Magnum refers more to pressure not velocity. (unlike said above)
2. Magnum primers are only needed for hard to ignite powders like W296/H110. (like said above)
3. The manual isn't always right because most manuals list a Magnum primer for all powders they test in a caliber that includes the word Magnum in the name. It's unnecessary and I think it's done to make it simple for the testing.

If you are loading Magnum rounds with powders like W231, Unique, Universal, Herco and even 2400 use a standard primer. If you're loading W296/H110, HS-6 or HS-7 use a Magnum primer. The only other reason to use a Magnum primer is if you are going to use the ammo in VERY cold conditions, -20 or below...

[gboling]

I noticed that Lymans 49th edition and Hornady's 7th edition both used mag primers for all of their .357 loads but not for all of their .44 mag loads. I recently read ( but I do not remember where) that the use of Mag primers ensures a more consistent burn rate. That suggests to me that the .357 may produce a less consistent burn rate than the .44 mag. Possibly due to the smaller diameter of the .357 case, but that is speculation on my part.

It would be interesting if someone could prove or disprove this.

Many manuals recomend using mag primers only where specified in the load data.

[ArchAngelCD]

I've found using a standard primer with 2400 gives better results than with a Magnum primer and 2400 is considered a "Magnum" powder.

[Snapping Twig]

FWIW, pressure = velocity, so if I stated it incorrectly, my apologies. Any charge that can move a .357 bullet 1000 + fps would have higher pressure, so that's the way I look at it.

I've never had an issue using standard primers for magnum powders like W296/H110 and in fact I get a more consistent result doing so. Case sizing and crimp appear to be of more importance for ignition than primers in my experience.

[ArchAngelCD]

Originally Posted by Snapping Twig

FWIW, pressure = velocity, so if I stated it incorrectly, my apologies. Any charge that can move a .357 bullet 1000 + fps would have higher pressure, so that's the way I look at it.

I've never had an issue using standard primers for magnum powders like W296/H110 and in fact I get a more consistent result doing so. Case sizing and crimp appear to be of more importance for ignition than primers in my experience.

I wasn't trying to step on anyone's toes but what you said is both true and false. If you're using a slow powder you will probably achieve the velocity you are looking for without surpassing the pressure limits but if you use a fast powder the pressures will spike quite high of overcharged without the expected increase in velocity because the powder completes the burn long before the bullet exits the barrel.

[MMA10mm]

Excellent posts ArchAngel.