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Discussion Starter #1
Was thinking about making some low power 357 loads for the SP for the wife and looking in Hornady's manual they are using magnum primers in everything in the 357 magnum. Isn't that a bit of overkill?
 

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You do not need magnum primers unless you are using slow magnum powder. I had the same question when I first started loading .357’s. I like 6.5gns of unique with 158gn bullet. More than 38+p and less than 357 magnum. Kind of like a 3/4 magnum.
 

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Sr40ken, That's my major complaint with the Hornady manual. They do the same thing for 44 Mag and use exclusively magnum primers …. but not for 41 Mag???? The good news is ….. Hornady pressure tests each load they list so you won't go over SAAMI pressure standards. The bad news is …. you won't get published velocities with standard primers using the same powder charge.
 

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Discussion Starter #4
Thanks for everyone's input!
 

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Some powders in the .357 require a magnum primer, others work fine with a standard primer. I think that Hornady (and Lyman) use magnum primers for all powders so that you don't inadvertently end up with standard primers with powders that need a magnum primer. If you size and prime cases, and then load all of them immediately, you can adequately segregate the standard primed cases from the magnum primed cases. But if you size and prime a large number of cases but only load a portion of them, as I do, then you can mix up the standard and magnum primers. So I use magnum primers for all .357 loads, and use data that was developed for magnum primers.
 

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Sr40ken, That's my major complaint with the Hornady manual. They do the same thing for 44 Mag and use exclusively magnum primers …. but not for 41 Mag???? The good news is ….. Hornady pressure tests each load they list so you won't go over SAAMI pressure standards. The bad news is …. you won't get published velocities with standard primers using the same powder charge.
With the SP 3"I'm not gonna cry over velocity. lolol For high velocity stuff I like 296 or MP300 in my 20" '92. Actually thinking about the 135 gr Speer Gold Dot as it has great expansion with 38 velocities for my carry round. However at this point I just need to learn the habits of our new SP101. I have a bunch of Xtreme and Powerbond 125 plated to get in the groove with.
 

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Magnum primers aren't necessary for most handgun powders...even 2400.
Most manuals will mention when Magnum primers are necessary, although many folks use Magnum primers all the time with proper load adjustments.
 

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You don't NEED magnum primers for Unique , it ignites quite easily , but you can use them , just follow the data in the Hornady manual .
I have read that magnum primers "might" help Unique burn a little cleaner but I've never tested the theory .
Good to have magnum primer loading data...there was a time when all the pistol primers that I could find were magnum...the Hornady Manual takes the mystery out of load adjustment with them .
Gary
 

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I had some erratic ignition with light loads of HP-38 (Same powder as Win 231) in 45 Colt. They all went boom but some shots were noticeably lighter than others. In fact a couple of shots didn't even make a clean hole in the backer but tore it. Magnum primers will help with consistent ignition in such circumstances.
 

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I had some erratic ignition with light loads of HP-38 (Same powder as Win 231) in 45 Colt. They all went boom but some shots were noticeably lighter than others. In fact a couple of shots didn't even make a clean hole in the backer but tore it. Magnum primers will help with consistent ignition in such circumstances.
Another good use of magnum primers. 231 doesn't take up much room in 45 Colt case and might be sensitive to position in the case . The magnum primer seems to help with consistent ignition in this case (excuse bad pun) .
Gary
 

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Use faster burning powders for weak ammo. Something like bullseye, titegroup or 700x make soft shooting weak ammo.
 

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SafetyJoe, Just to set the record straight ….. fast burning powder is NOT weak. It can generate very high chamber pressure with just a small charge weight. Yes, fast burning powder is used for light target loads (low velocity or "weak as you call it) by using very light charge weights. As an example, a 38 Special target load with a 148gr LHBWC uses only 3 gr of Bullseye powder yet it generates about the same chamber pressure as full power loads.

DrHenley, For 45 Colt light loads, HP-38 seems to work very well. Keep in mind …. a 45 Colt factory load only generates a max chamber pressure of 14,000 psi. Nearly all faster burning powders don't burn well until chamber pressure is at least 15k psi. To compound problems, a 45 Colt case is huge compared to the powder charge where a 14k psi load (7gr HP-38, standard primer, and a 250gr lead bullet) only occupies about 1/3 of the case capacity. This often results in position sensitivity, meaning erratic velocities depending on how the powder lies in the case. Magnum primers do help but they increase chamber pressure so it's wise to back off the powder charge by 1/2 grain.
 
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