Unique powder primers

M

montana09

New member
Quick question, do you need to use small magnum pistol primers when reloading with Unique powder for .357 magnum or would regular Winchester small pistol primers work? My manual doesn't have a recommendation and Alliant's website lists CCI 500 primers with 125 gr GDHPs and Unique so would any small pistol primer work or do I need CCI 500's
 
Some reloading manuals list magnum primers, and some list standard small pistol primers with Unique. Either one can be used, the magnum primer is not required. Best practice is to use the type of primer recommended by your reloading manual for the given powder charge. Many sources will say that magnum primers are only required in the 357 Magnum for hard to ignite powders like W296/H110 and that standard primers are sufficient for most other powders. The reloading manuals I have are split about equally in using magnum primers across the board for the 357, versus the others that use non-magnum primers for some powders and magnum primers for other powders.
 
With the .357 Magnum (and many other magnum cartridges), the powder being used determines whether a magnum primer should be used or not. Unique does not require a magnum primer. Powders used in the .357 Magnum in which a magnum primer should be used are HS-6, W296/H110, and IMR4227. Hope that helps.

Don
 
Just a note in case you're new to reloading: the term "magnum" used in something like .357magnum or 44 magnum has nothing to do with primer requirements. The requirement for a magnum primer is based on the powder being used. Some non "magnum" loads require the use of magnum primers because they use powder that requires it to ignite properly. Some "magnum" loads don't require magnum primers because they are being loaded with powder that doesn't require it. Coatings on some powders require the use of magnum (hotter) primers to get the ignition started efficiently. Using magnum primers in loads that don't require it can raise the pressure of the load some as a result of this substitution. As stated, follow the loading manual's recommendation.
 
But keep in mind it really isn't always just the powder. Even with easy-to-ignite powders, if your charge leaves a lot of empty space in the case a magnum primer may improve ignition consistency and lower SD's. But it can also do the opposite with some loads, so this is something that has to be tried to determine whether or not it is so for your gun and load.

I've seen that improvement occur mainly in rifles, like .30-06 with Garand loads of single-base stick powders that don't fill the case well. But it can happen in any gun and if you have a chronograph you can measure the difference. If not, just look at what produces the tightest groups off bags.
 
With Unique I always use standard CCI standard primers.

I did a back to back test with Unique in .45 Colt and got better results with the standard primer:

8.5g Unique, 255g SWC, CCI-300, 977fps, 17 SD, 56 ES, 15 shots
8.5g Unique, 255g SWC, CCI-350, 985fps, 21 SD, 82 ES, 15 shots

As said above it depends on the powder. I chronograph and target will help show you which to use too :) .

Note when I tested back to back with Universal, CCI-300 load had an 44 ES, CCI-350 88 ES.

Another words it pays to test your loads. Some powders though do need to use a magnum primer.
 
The mag primer may have a thicker cup. Less chance of a pierced primer. I use mag even in 38 spec.

Unique doesn't care what primer. Only ball powders do.
 
Unique doesn't "need" magnum primers...it ignites quite easily.
If you have magnum primers , or used magnum primers by mistake it's OK , you'll pick up a few extra fps and as long as it's not a maximum load I doubt you will notice any difference. Check accuracy against your regular loads...they could be bettor or could be worse .
Gary
 
Unique does not need magnum primers, but, your 357 magnum loads do.
You have a longer powder column than non-magnum 38 special, and higher chamber pressure.
If the published data used magnum primers, you should, too.
If you use regular primers, catastrophe is unlikely. They will go bang and launch you projectile.
 
Unique does not need magnum primers, but, your 357 magnum loads do.You have a longer powder column than non-magnum 38 special, and higher chamber pressure.
If the published data used magnum primers, you should, too.
Click to expand...

I'm sorry, but that is just not true. It has nothing to do with the particular cartridge, it has everything to do with the powder. Unique does not require a magnum primer, unlike something like W296, which does. You may use one, but it's not doing you any favors. Period.
 
When the folks who publish reloading data use a magnum primer in the data the load is tested with THAT primer. In some cases, I have seen data that indicated that the pressure is as much as 5,000 cup higher with a magnum primer than with a standard primer. So unique is a medium/fast burn rate powder and will ignite easily with a standard primer. But if you want a max magnum load use the magnum primer.

As others have stated here if you are using a target load that is not max pressure then try the regular small pistol primer and the magnum primer and see which gives you better results.

For other powders that have a slower burn rate like 296 always use a magnum primer to ensure complete ignition.
 
Last edited:
Published data that developed using magnum primers, require use of magnum primers.
Otherwise, you are not using that published data.
Personal opinions about Unique needing, or not needing magnum primers do not override tested published data.
Tell it to Alliant.
 
Those saying magnum primers are ALL ABOUT THE POWDER need to read this article by a primer designer. It's not only about the powder. It's also about empty air volume in the case. Before CCI's reformulation in 1989 to increase spark heat and duration for high deterrent spherical propellant ignition, it was all about the volume, as magnum cases have more volume than non-magnum cases. Magnum primer: Magnum case. That's where the name came from. If a powder is fast enough, though, even in a magnum case it doesn't usually need a magnum primer to perform, as rclark's tests show.

The main downside of magnum primers in smaller cases is that because they make more gas, they can start unseating a bullet before the powder is burning well, and this can make velocities and ignition erratic. The .22 Hornet is famous for having this problem, but you see it in handgun cartridges, too. It is one reason why, in some cases, magnum primers actually produce lower velocities and pressure. So if you do try a magnum primer, I would not rely on a taper crimp. I would use a stiff roll crimp just as you would with warm loads.
 
The .22 Hornet is famous for having this problem, but you see it in handgun cartridges, too.
Click to expand...

I can vouch for that. AND, it is exactly the reason that folks in the know have reverted to using small PISTOL primers in the 22 Hornet, including myself.
 
"...Hodgdon on line Data shows Magnum Primers for all their .357 magnum loads..." Which is nonsense. Magnum primers have nothing whatever to do with the cartridge. They're about the powder and nothing else. Unique does not require magnum primers.
That Shooting Times rag article about CCI primers proves nothing either. .38 Special loads work just fine in a .357 case with a regular primer.
Then there's this: "A large-capacity case, a heavily deterred propellant, or extremely cold weather (less than 20 degrees Fahrenheit) typically makes the Magnum primer desirable." A .357 isn't exactly a large capacity case.
 
You must log in or register to reply here.
Back
Top