Magnum primer questions?

Prof Young

New member
Loaders:

How are magnum primers and standard primers different?

If someone "accidentally" bought a brick of small pistol magnum primers (he wasn't paying attention that day), would it be dangerous for him to use those in standard loads?

Life is good . . . and pay attention!
Prof Young
 
My very first loads were done with CCI Small Pistol Magnum primers that I, too, picked up by accident. As a brand new loader, a mere 11 months ago, I had never bought primers, powders, or bullets. Cabela’s shelves were pretty barren of anything pistol, so I gleefully grabbed the only pistol primers I found. I compounded my error by immediately loading up 100 rounds, though I started on the low end of HP-38 with a box of Berry’s 115gr CPRN in 9mm.

I took a tremendous reaming from the forum members before receiving some good coaching.

Magnum primers burn hotter than standard primers. As a result, no...you cannot use them in standard loads. It would be best to set them aside and pick up the proper primers. However, you can use them in adjusted loads, meaning, start at absolute minimum charge and work up. Also, don’t get aggressive with seating and crimping bullets. Basically, use with a proper amount of caution, and then, only if you absolutely refuse to get the proper primers.

FWIW - I still have 900 CCI 550s, Small Magnum. After shooting the rounds I loaded in error, after confirming that I was loading long, bare minimum crimp, and at the bottom of the load range, I put the magnums away and never looked back.

I know that some are more cavalier about using Magnum primers for small pistol loads...but I’m not one of them.
 
I would be reluctant to use magnum primers with fast powders such as Titegroup, Bullseye, 700X and so forth.

If you are using powders that are some what slower, drop powder charge 10% and start from there.
 
How are magnum primers and standard primers different?

They simply have a slightly hotter burn and are typically used with harder to ignite ball powders. While they may not be ideal with some flake powders, unless you are on the bleeding edge of a maximum load, they aren't going to hurt anything.

Don
 
From my understanding they burn hotter, and just so slightly longer.
If your doing plinking loads, and not near max powder charge you should, should be ok.
I had gotten them by accident when i was loading 40 S&W.
Ended up using the rest of them for my 45ACP with small primer pockets.
Shooting LSWC at 800 fps there were no issues.
 
Various people have written that magnum primers can (not will, but can) raise the pressure of a load as much as 15%.

In some cases this can give undesirable results, but it would be a truly unusual case if it gave dangerous results. As noted, you can adjust the load for magnum primers, but its best to just get the right stuff, and sell or trade the unsuitable stuff.
 
USSR:
They simply have a slightly hotter burn and are typically used with harder to ignite ball powders. While they may not be ideal with some flake powders, unless you are on the bleeding edge of a maximum load, they aren't going to hurt anything.

That is my thinking also having been there and done that.

Ron
 
I agree with "unless you are on the bleeding edge of a maximum load, they aren't going to hurt anything". Talking Revolvers loads here... I've done back to back tests over the chronograph with several powders that I use just for my knowledge and came to that conclusion. But accuracy could be affected. For example using a Magnum primer of one powder, doubled the Extreme Spread of the standard primer load. In another powder the Extreme Spread only changed from 28 to 27. You will sometimes get a bump in velocity, sometimes less with a Magnum primer. Results surprised me sometimes. In some cases it 'cemented' the fact that yes, with 'this' powder a Magnum primer should be used. In another, the standard primer should be used.... Chronographs are simple, but very useful devices. My tests were with CCI brand of primers BTW.
 
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Thanks for the info.

Loaders:

Thanks for all the info. Good to know.

I've got plenty of access to standard primers, and I do load some 357 magnums so I have a use for the magnum primers. It's just that with a whole brick . . . I'm gonna have mag primers for a looooong time.

Life is good.
Prof Young
 
I've got plenty of access to standard primers, and I do load some 357 magnums so I have a use for the magnum primers. It's just that with a whole brick . . . I'm gonna have mag primers for a looooong time.

You can never have too many primers. :)

Ron
 
Since the same primers, standard/magnum, can easily differ by brand, One brand of magnum primer can be the same as another brands standard primer. I mostly use them interchangeably except when particular powders recommend magnums.
 
Prof Young,

The term Magnum Primer originally means a primer for a magnum case. Magnum cases are larger than standard cases, as the name implies, so they hold more powder. Since the empty airspace in a case full of powder is the space between the grains, you can see that magnum cases will have more total empty space in them than standard case sizes do, even when the loading density is 100%. Progressive powders, especially the slower ones typically used in magnum cases, require a minimum amount of pressure to start and maintain burning. Even though they release their own oxygen during combustion, they don't release enough to burn all the fuel available from the same molecules (the reason you get unburned carbon left over in the barrel), so if they don't have adequate start pressure and temperature they don't liberate oxygen from the nitrocellulose fast enough to sustain the reaction and they can actually squib out (extinguish in the case).

So, what magnum primers did originally (and still do) is make more gas to better pressurize the larger amount of empty space in a magnum cartridge to sustain ignition. Because of the relationship between temperature and pressure, keeping pressure higher also keeps the temperature higher. This means, by the way, that in a non-magnum case that has a lot of empty space due to poor case fill by the powder charge, a magnum primer may also be provide best ignition consistency.

In 1989 CCI took the magnum primer concept a bit further. They had noticed that even with adequate pressure from a primer, the very heavy deterrent coatings on the spherical propellants developed for the military in the 1960's (sold today as HS-6, H110, H335, BL-C(2), H380, H414, U.S 869, 296, 748, 760, and still using the unchanged 1960's formulations) had such heavy deterrent coatings that they resisted ignition even with adequate pressure. So CCI added metal powder and barium oxidizer to create a very hot white spark shower that would more reliably get these powders burning. It significantly reduces muzzle velocity variation in some instances, so the recommendation came to be made that these primers should be used even in non-magnum cases when those powders are employed.

Problems with using magnum primers:

Some benchrest competitors complain that the more pressure the primer makes, the less they are controlling it with their powder charge and that increased velocity SD can result. Obviously, this applies mainly to stick powders and other easy-to-ignite powders in loads with good load density.

In very small powder spaces (the .22 Hornet is famous for this problem, as are some pistol cartridges) a magnum primer can make enough pressure to start unseating the bullet before the powder burn gets seriously underway. This can actually increase velocity SD. The way to tell is to try both magnum and standard primers with a starting load of your powder of choice and shoot them over a chronograph and then choose the primer that produces the lowest velocity SD.

Pressure can change. Due to the bullet unseating issue, magnum primers can actually reduce peak pressure in some loads. Mostly, though, it either stays about the same or goes up, as is determined by an increase in measured velocity. Typically, in cases that use large rifle primers, the difference is rather small and not enough to justify adjusting a load unless the velocity shift reduces your group size by moving you off a barrel time sweet spot. In cases using small rifle primers, you usually seem more effect from shifting from standard to magnum primers. I've seen about 11% pressure increase change in one instance in the .223 Remington.

This article is worth reading.
 
I've read that magnum primers use a slightly thicker shell, and utilize a longer duration ignition to completely burn the larger quantities of powders. The debate over std vs mag primers has been argued for decades with no decisive conclusion. I generally see no change from using mag primers in place of std with supersonic smokeless loads. I do however observe some less measured SD's (standard deviation) with my smokeless subsonic, and my black powder 45-70 loads.
 
Road Clam said:
I've read that magnum primers use a slightly thicker shell, and utilize a longer duration ignition to completely burn the larger quantities of powders.

Some of the small rifle magnum primers have thicker cups. But the new (relatively) Federal GM205MAR is a standard primer with which Federal told me they thickened the cup on to achieve military sensitivity spec. All large rifle primer cups seem to be the same.

As to longer duration, it varies with the primer. Allan Jones says there isn't a universal pattern to it. Some makers just put a larger quantity of their standard priming mix in their magnum primers. Others leave the sensitizer quantity the same, but add more fuel compounds to be burned once the the thing lights up. When CCI raised the spark temperature in 1989, they were eventually followed by all the domestic makers and now even the standard domestic primers seem to have that. A number of foreign primers, standard or magnum, do not.

The only thing they all have in common is that they generate a larger volume of gas than the standard versions do, and if you have larger capacity cases or low loading density in a medium power cartridge, either way there is a lot of empty air space to pressurize and that's what magnum primers are universally designed to do. Spark temperature, brissance (speed of ignition) and the rest are all variables.

The debate over std vs mag primers has been argued for decades with no decisive conclusion.

And there won't be one, either, because they keep changing them, unannounced, over time. That's what Jones said and it is indirectly verified by QuickLOAD's author. At one time, he and Mic Mcpherson were working on adding primer choices to the program, but that seems to have been abandoned because of the changes. The same for load manuals. You don't see lists of different primers and their effects because they keep changing order.

About the best thing one can hope to do is find a lot of primers that works exceptionally well with your pet load and buy enough of that lot at once to last as long as you think you'll want to use that load. They don't seem to go bad.
 
Great stuff Unclenick, thanks.
They had noticed that even with adequate pressure from a primer, the very heavy deterrent coatings on the spherical propellants developed for the military in the 1960's (sold today as HS-6, H110, H335, BL-C(2), H380, H414, U.S 869, 296, 748, 760, and still using the unchanged 1960's formulations) had such heavy deterrent coatings that they resisted ignition even with adequate pressure. So CCI added metal powder and barium oxidizer to create a very hot white spark shower that would more reliably get these powders burning. It significantly reduces muzzle velocity variation in some instances, so the recommendation came to be made that these primers should be used even in non-magnum cases when those powders are employed.
I always wondered why HS-6 was such a SOB to get burning.
The Winchester WSPM small pistol mag primer seems to a great job with HS-6 in 357 and 9mm.
 
My opinion of no difference between std and mag primers was tested and the claim was put to bed when I loaded up 10 rounds of 460 S&W mag handgun using the Hornady 200FTX and 50gr of H110 powder. I ran both std and mag primers and observed no measurable differences in precision or velocities. Some loaders claim that they see an advantage using mag primers with ball powders in rifle. Again I loaded up some .223 55gr with W748 for my AR-15 Varmint both std and mag primers and same deal no measurable losses or gains.
 
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