Magnum primers in .357 magnums

[Walt]

In Handloader magazine #331 (April 2021) Brian Pearce wrote an article, ".357 Magnum (Rifle)" regarding the limitations of using magnum primers vs. standard primers.

He states; "...many of the loads (listed in his Pet Loads article) utilize standard primers rather than magnum. Magnum primers will increase pressures, sometimes as much as 8,000 to 10,000 psi. Good examples include Alliant 2400 and Accurate #9 powders. When 2400 is loaded in conjunction with the 158 grain XTP-HP Hornady bullet and is capped with a CCI 550 Magnum primer, it reaches maximum pressure at 12.8 to 13.0 grains and velocity is approximately 1475 fps from a 20" barrel. By simply changing to a CCI 500 primer, pressure drops nearly 10,000 fps. The powder charge can then be increased to 14.8 to 15.0 grains for just under 35,000 psi and velocity increases to around 1750 fps. Switching to Accurate #9 powder and using the same 158 grain Hornady bullet with CCI 550 Magnum primers, maximum pressure is reached around 13.8 grains which yields just under 1700 fps. By changing to a standard CCI 500 primer, the powder charge can be increased to 14.9 grains for 35,000 psi and velocity jumps to around 1825 fps.

[Scott Tschirhart]

I’ve used small rifle primers with 2400 in the .357 for more years than I can remember.

[JimT]

I have been using Small Rifle and Magnum primers in my .357 loads since the early 1960's.

[Scott Tschirhart]

I have been using Small Rifle and Magnum primers in my .357 loads since the early 1960's.

Heck, I probably learned this from you Jim.

[JimT]

I have been know to encourage bad habits ....

When a teenager I worked up to this load and used it for years. Still shoot it now and then.

Lyman #358429 .. the Keith 173 gr. SWC
14.5 gr. 2400
Small Rifle Primer

[Grizz]

Thanks Walt

that's worthwhile info to add into my log book.

[earlmck]

Uh -- guys -- I think you'll find that the small rifle primer is the small pistol magnum primer. If you mean to use a standard pistol primer you need to get the small pistol primer.

My main powder used in the 357 is something labeled H108 which was (I'm pretty sure) just a run of the WWII surplus 30 carbine powder that tested out a little warm so couldn't be labeled as H110 like the original Hodgden stuff. I learned from a couple (I'm a slow learner) "failures to ignite" that I needed the magnum primer for this powder. So I use small rifle primers. Years ago I used 2400 and then switched over to Blue Dot and just used standard small pistol primers for those stalwarts.

Years ago one of my buddies found us this "deal" on the H108 for something like $8/jug and I tried to lay in a lifetime supply but am on my last jug (so hope it wasn't really a "lifetime" supply). Don't know what I'll use when the H108 runs out but probably Lil' Gun. I don't know if Lil' Gun requires magnum primers but I know it doesn't object to the rifle primers.

[GunnyMack]

Always been my understanding that a magnum primer was ' needed ' for large volumes of powder and ball powders more so.
But like most, mag primers got used if the cartridge is labeled as a MAGNUM, what I've always used in 44 mag. I'm not sure I've ever loaded 357s...?

[Walt]

Grizz, thanks for your appreciation of the thoughtful and informational intent of the article.

[earlmck]

I should also add in my "Thanks Walt!". That is really interesting. And even though I must have read the article when it came out it failed to register at the time. That is an unexpected result that needs to be filed away in the brain pan a while for future use.

[Walt]

You're welcome, Earl!

[TedH]

Uh -- guys -- I think you'll find that the small rifle primer is the small pistol magnum primer.

This is correct. CCI small pistol magnum primers are small rifle primers in different packaging. This is according to an un-named friend that has worked at the factory for years.