Primer questions for reloading .357 mag

[Karys]

I'm going to work up a .357 load this weekend. I'm using Alliant Unique and I'm loading a 158 grain Rainier plated flat point. Since I'm using a plated bullet, I'm not planning on driving them all that fast. I chose Unique for powder because it has a pretty wide range between the bottom and the max.

Anyway, in the Alliant reloading guide, they use the Federal 200 primers, which is a small magnum pistol primer. Here's my questions:

Do I have to use a magnum primer?

Since I'm starting from the bottom, could I use a CCI 350 or CCI 300 primer instead?

Thanks for any input. This is the first time I'm reloading .357 magnum and I want to make sure I'm safe.

[mauser]

I've never used magnum primers in my .357 Magnum loads, nor have I ever used Unique powder for that caliber. I always use CCI 500 Small Pistol Primers with various powders. You can't use CCI 300 or 350 primers, they're large pistol primers, they won't fit.
That being said, if you are going to be working with a light load, you can substitute a different brand of primer, and certainly a non magnum primer. I'd be wary of using a non magnum primer with the lightest loads, just in case you end up with a squib* load, (It's unlikely, but I'd cautiously try a just a few just to be sure). If you're working near the middle of the recipe, I'd think you'd be safe in any event.
FWIW, I'd never substitute a magnum primer into a recipe that specifies a regular primer. If for some reason I would decide to try something like that, I would start real light, as in minimum load. Even then I'd be very cautious.
To be safe, never start out with a maximum load and never make substitutions at maximum loads, always start out lighter and work your way up, being mindful of pressure signs.

*Squib according to Wikipedia.
A squib load, also known as a squib round, pop and no kick, or just a squib, is a firearms malfunction in which a fired projectile does not have enough force behind it to exit the barrel, and thus becomes stuck. This type of malfunction can be extremely dangerous, as failing to notice that the projectile has become stuck in the barrel may result in another round being fired directly into the obstructed barrel, resulting in a catastrophic failure of the weapon's structural integrity.

[harleyspring]

Mauser hit it on the head.
the only thing i wanted to add is that if by chance you using an automatic- desert eagle or coonan or whatever, the light loads will not cycle. any time i try something new, in an automatic or revolver or all of them actually, i'll only load a handfull and see how they perform. sometimes i load a handfull with a couple different loads and see what i like best.

[Karys]

I'm thinking I'll go with small magnum pistol primers since I'm starting at the bottom and working up to the middle or just above the middle. I'm not looking to build really light loads; I just don't want to max them out with a plated bullet.

The guns I'll be shooting are two Rugers, a GP 100 and a Blackhawk, so cycling the slide of a semi-auto isn't an issue.

Thanks for the help guys. I think I'll be fine.

[ArchAngelCD]

Just because you are loading a Magnum rounds doesn't mean you have to use a Magnum primer. You only need a Magnum primer when you charge hard to ignite powders like H110/W296. With those powders it's highly recommended you use a Magnum primer. Unique isn't hard to ignite so you don't need a Magnum primer.

[manyplews]

Being pretty poor when I got married,I shot nothing but the Ray Thompson gas check bullet in my S&W 28 N-frame (Lyman U358156) for many years.
I used fairly stiff loads of Unique powder and the regular CCI small pistol primer.
With my own cases,I could load 357's cheaper than I could buy .22 LR ammo.
Never had a problem with leading,using the gas checks.Per my records,I used over 3000 of these cast bullets.
You can get about 900 loads out of a pound of Unique.
Just scan the powder levels in your cases as they stand in the loading block before you start seating bullets.If you accidently double-charge a case,you can pick it out easily.
A year or so ago,Ken Oehler had an article in Shooting Times with data showing significant velocity changes just from changing the position of Unique powder in .38 Special reloads - powder to the rear vs powder to the front.
Ron

[chalmitch]

I'm thinking I'll go with small magnum pistol primers since I'm starting at the bottom and working up to the middle or just above the middle. I'm not looking to build really light loads; I just don't want to max them out with a plated bullet.

The guns I'll be shooting are two Rugers, a GP 100 and a Blackhawk, so cycling the slide of a semi-auto isn't an issue.

Thanks for the help guys. I think I'll be fine.

I began reloading in the 80's. The only primer then recommended for a .38/.357 was the SMALL PISTOL primer. There is no need for a rifle or magnum prime rin this caliber.

Best regards,
chalmitch

[Farbmeister]

Ball powders *generally* require magnum primers due to their difficulty in lighting.

Magnum primers burn hotter and longer to get ball powders started.

If it calls for it, and its a ball powder, USE THEM... otherwise you may end up with a slug half an inch down the barrel and a case still half full of powder.

[deafsmithco]

Ball powders *generally* require magnum primers due to their difficulty in lighting.

Magnum primers burn hotter and longer to get ball powders started.

If it calls for it, and its a ball powder, USE THEM... otherwise you may end up with a slug half an inch down the barrel and a case still half full of powder.

While it is always recommended to follow the manufacturer's loading data, I have to question Alliant's choice of primers on this. I have never used a magnum primer with Unique and don't plan on it either. If you look at some other loads Alliant lists, you will see what I mean.

357 Fed. 200 6.5 Bullseye 158 LSWC. Why a mag. primer with Bullseye?

38 Spl. Fed 100 4.3 Unique 158 LSWC. I guess you need a mag. primer to light that extra 2.5 grains of powder in the 357 case. (6.8 in the 357 load).

In the .44 mag they use a Fed 150 with every thing, except the Swift bullet loads.

Of course, I don't have a lab with pressure testing equipment and I don't know why they used the primers they did. I do think a mag. primer with Unique is over kill.

[Farbmeister]

I've read that some combinations require that your point the muzzle in the air to get the powder to lay against the primer so it ignites. Positional powders? Large volumes with small amounts of powder? Unless you have tested the combo out in your gun.. do what the book says as it been tested and works.

I use 5gr of Bullseye with a regular CCI primer and never had a problem.. they just go bang. Its not a magnum load, but cheap and accurate.

But with about 12gr WC820 (ball) without the magnum primers I HAVE had a bullet half an inch in the barrel and all the powder wedged in behind it. SO I know that that powder needs a magnum primer or I spend all day hammering bullets out of the barrel.

I also think that reloading manuals will never, ever have the same loads for the same components. I don't know why. Most of the 'book loads' people post are not in the Lee manual I have. And they are from manufacturers, also.

Go figure.