357 Magnum primers ?

R

rebs

New member
I have 100 357magnum cases sized and primed with magnum primers. Would it be safe to load them light with 2.7 to 3.2 of bullseye powder with a 158 gr
LSWC's ? Or would I have to load them with a magnum charge because of the magnum primers ?
 
Keep your starting load at least 10% below max to start and check for pressure signs...you probably won't find any with this light a load. Substituting mag primers in max loads where magnum primers aren't called for definitely calls for backing off and working your way up. It's not that big a deal. I use mag primers for almost all .357mag loads.
 
Assuming you're using magnum brass, 2.7 Bullseye is very light. Most data starts around 4 or more.

Faster flake powders like Bullseye and Unique work fine with standard or magnum primers, as long as your work up your loads from the recommended starting point.

Magnum primers are really only needed with some slower powders, I don't use HS-6 in 357 without them.
 
Start with the book starting loads. Magnum primers will give a bit more pressure/velocity, but, don't start guessing at powder charges (at least for a few thousand rounds of experience is gained). A starting load, even with Magnum primers is safe.
 
You sure can. If you have a box of Winchester pistol primers it states on the box for magnums. It won't make a difference for standard or magnum rounds
 
A starting load, even with Magnum primers is safe.
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I agree. With what you're doing, using a magnum primer would hardly even be noticeable. I've done it myself. During the shortage, I ran out of standard primers. I loaded my target 38's and 357's with mag primers with no hesitation whatsoever. Didn't even adjust the powder charge. The difference was "transparent."

Or would I have to load them with a magnum charge because of the magnum primers ?
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This is frequently a point of confusion for the novice loader. The need of a magnum primer is largely a function of the propellant - not whether or not it's a Magnum case and/or Magnum level loading.

Difficult to ignite propellants such as W296/H-110 or HS-6 should get a mag primer in revolver cases.

Revolver cases being long (especially the Magnum variety - but the Specials too), with a lot of space inside, should get the mag primer when using difficult to ignite powders.

Semi-auto cases, being shorter, need not, basically. For instance, HS-6 gets a mag primer in revolver loadings, but not in semi-auto loadings. W296/H-110 would be a moot example however; because you wouldn't use such a slow powder in a semi-auto anyway.
 
For a cast 158 out of a .38 Special, 2.7 is below minimum with Bullseye. 2.7 of Bullseye is the standard .38 Special 148 grain WC load. NOT a 158.
3.2 is the Start load for a cast 158. 3.5 is Max. .38 Special loads are fine in a .357 case though.
A cast 158 grain .357 load uses 4.3 to 4.8 of Bullseye.
Magnum primers have NOTHING to do with the cartridge, the load or type of bullet used. They're ONLY about the powder used.
Mind you, having 100 cases primed with magnum primers means use the 100 case primed with magnum primers. It's not going to cause you any grief not matter what powder you use. But use the correct data for the cast bullet weight.
"...W296/H-110...wouldn't use such a slow powder in a semi-auto..." W296/H110 was created for use in the .30 Carbine. Including pistols in said cartridge.
 
The primers won't be an issue, but I would highly advise staying above minimum load. Should be around 3.5 grains of Bullseye in a mag case.
 
the 10% below max rule is not allways a good idea. Some times with powder like H110 there is only 1 grain difference in a minimum and max load.
 
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