Mag primer?

Fullthrottle · November 10, 2009, 10:26 PM

OK I am new to reloading and have stuck to what the manual says. So far only loaded .38spcl.
I went to my local gun store to purchase more primers, one of the sales ascociates made a comment about using small pistol magnum primers for loading .357 magnum loads. The Lee load manual I have states small pistol primers, not magnum. I left with only small pistol primers, they have more magnum than regular, was wondering if magnum was safe for .357 mag or if he was trying to move them off the shelf. Does it matter for that round?

Shoney · November 10, 2009, 10:37 PM

Yes you can use SP mags in a 357, but you must be aware that they will most likely increase the pressure. So to be on the safe side, always reduce the load to the start level and work up, watching for pressure. I have subbed them into 357 with ball powders, but never loaded them to max charge.

SL1 · November 10, 2009, 10:46 PM

Magnum primers are not usually necessary in the .357 Magnum, except for some hard-to-ignite powders like H-110/WW-296.

But, some manuals, especially old ones, used magnum small pistol primers for ALL loads. So, the idea persists with many people.

Using magnum primers can increase pressure, so it is best to follow the data that was pressure-tested, using whatever primers the data used. If you can't get the standard primers when the load data calls for it, you CAN substitute magnum primers, but you definitely need to go back to the "start" load and work-up again.

SL1

T. O'Heir · November 10, 2009, 10:56 PM

The sales associate is confused. Magnum primers have nothing to do with the cartridge. They're about the powder used. They burn a bit hotter for a bit longer. They're made to light hard to ignite powders and for cold weather shooting.
The .357 Mag uses small pistol primers. If you opt for magnum primers, you'll have to work up the again.
If you're shooting .38's out of a .357 revolver, you can load .357 brass to .38 velocities with no fuss. Eliminates the lube gunk ring that builds up in the cylinders when using .38 brass.

Fullthrottle · November 10, 2009, 11:05 PM

Thanks for the info. I failed to state that so far I only have loaded starting loads(for now that is fine by me). I have been using IMR SR4756 as it was readily available to use in both .38spcl and .357 mag acording to the Lee loading manual.

T. O'HEIR: The sales guy did mention that he loads .38 in .357 for that reason too.

November 10, 2009, 10:26 PM	#1
Fullthrottle Senior Member Join Date: October 24, 2009 Posts: 280	Mag primer? OK I am new to reloading and have stuck to what the manual says. So far only loaded .38spcl. I went to my local gun store to purchase more primers, one of the sales ascociates made a comment about using small pistol magnum primers for loading .357 magnum loads. The Lee load manual I have states small pistol primers, not magnum. I left with only small pistol primers, they have more magnum than regular, was wondering if magnum was safe for .357 mag or if he was trying to move them off the shelf. Does it matter for that round?

November 10, 2009, 10:37 PM	#2
Shoney Senior Member Join Date: February 21, 2002 Location: Transplanted from Montana Posts: 2,311	Yes you can use SP mags in a 357, but you must be aware that they will most likely increase the pressure. So to be on the safe side, always reduce the load to the start level and work up, watching for pressure. I have subbed them into 357 with ball powders, but never loaded them to max charge. __________________ I pledge allegiance to the Flag - - -, and to the Republic for which it stands….Our Forefathers were brilliant for giving us a Republic, not a democracy! Do you know the difference??? and WHY?http://www.wallbuilders.com/LIBissue...les.asp?id=111

November 10, 2009, 10:56 PM	#4
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	The sales associate is confused. Magnum primers have nothing to do with the cartridge. They're about the powder used. They burn a bit hotter for a bit longer. They're made to light hard to ignite powders and for cold weather shooting. The .357 Mag uses small pistol primers. If you opt for magnum primers, you'll have to work up the again. If you're shooting .38's out of a .357 revolver, you can load .357 brass to .38 velocities with no fuss. Eliminates the lube gunk ring that builds up in the cylinders when using .38 brass. __________________ Spelling and grammar count!

November 10, 2009, 10:46 PM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Magnum primers are not usually necessary in the .357 Magnum, except for some hard-to-ignite powders like H-110/WW-296. But, some manuals, especially old ones, used magnum small pistol primers for ALL loads. So, the idea persists with many people. Using magnum primers can increase pressure, so it is best to follow the data that was pressure-tested, using whatever primers the data used. If you can't get the standard primers when the load data calls for it, you CAN substitute magnum primers, but you definitely need to go back to the "start" load and work-up again. SL1

November 10, 2009, 11:05 PM	#5
Fullthrottle Senior Member Join Date: October 24, 2009 Posts: 280	Thanks for the info. I failed to state that so far I only have loaded starting loads(for now that is fine by me). I have been using IMR SR4756 as it was readily available to use in both .38spcl and .357 mag acording to the Lee loading manual. T. O'HEIR: The sales guy did mention that he loads .38 in .357 for that reason too.