Magnum vs regular primers

[Paddy]

I know magnum primers are suggested/ required for some loads. What is a circumstance when a magnum primer would not be a good idea? Seems like a hot complete burn is always desirable is it not? Even if it requires reducing the powder charge a bit.

 

[ArchAngelCD]

I know magnum primers are suggested/ required for some loads. What is a circumstance when a magnum primer would not be a good idea? Seems like a hot complete burn is always desirable is it not? Even if it requires reducing the powder charge a bit.

If hot is good hotter is better? NO!

In handguns loads sometimes magnum primers can cause wide swings in velocities like when used with 2400. Not every load with magnum in the name needs a magnum primer. H110/W296, HS-7 and HS-6 are the powders I know that really should be used with a magnum primer. They are hard to ignite ball powders and perform much better when set off with a magnum primer, especially in the cold.

If you're asking about rifles we can talk about that too.

 

[fiftybmg]

You want magnum rifle primers for slow burning rifle powder.

Slow is relative with powders, and primers of different make have differing heat outputs, so for rifle a 'magnum' primer does the job, irrespective of caliber.

The primer affects the pressure curve in the case just after ignition. With slower powders it raises the curve, which is not needed with fast ball powders in pistols.

Because changing the primer can change the pressure in the case, apply due dilligence when doing so for rifles.

For pistols it seems to make no practical difference. I've used PMP primers for small pistol that are designated 'magnum', and can't tell the difference with primers not marked 'magnum'. The Muron small pistol primers gave me slightly higher than average velocities, and they were not marked as magnum.

So to answer the question, when is a magnum primer not a good idea, I'd have to say only in the case of semi-auto pistols that use a large primer [ 10mm, 45ACP ], don't use magnum rifle primers in case you send the pressure too high too fast.

 

[ArchAngelCD]

USUALLY in rifle loads, you should use a magnum primers when the charge weights are 60gr or higher. It's not a rule, just a guideline.

 

[Paddy]

Okay good thx. I'm not loading any rifle over about 22gr right now so that's not an issue, however with the 300 blackout I'm reading that it's a good idea to run small magnum primers for small charges of slower powders (relative) to get a solid ignition and avoid SEE possibility or hang fires. Some guys are also drilling out their flash holes which is something I'd like to avoid because it sounds like a pain in the arse.

 

[ArchAngelCD]

however with the 300 blackout I'm reading that it's a good idea to run small magnum primers for small charges of slower powders (relative) to get a solid ignition and avoid SEE possibility or hang fires.

I don't know, the guys I know loading for the 300 Blackout are loading it more like a 30 carbine than a heavy rifle cartridge. they are using fast pistol powders like W296/H110 and Lil'Gun. Of course if you use W296/H110 a magnum primer would be a good idea anyway but I'm not sure about that slow rifle powder choice.

 

[Paddy]

Well, slow for blackout. Still fast for rifle. Some guys are using 4198 which seems about on the slowest end. My understanding is that it's a balancing act to get the cartridge to work in ar because faster powders burn so fast the gasses are collapsing before the bolt can cycle and the slower powders that will cycle the action are too slow to burn completely in shorter barrels and lighter charges that the case allows.

 

[ArchAngelCD]

Well, slow for blackout. Still fast for rifle. Some guys are using 4198 which seems about on the slowest end. My understanding is that it's a balancing act to get the cartridge to work in ar because faster powders burn so fast the gasses are collapsing before the bolt can cycle and the slower powders that will cycle the action are too slow to burn completely in shorter barrels and lighter charges that the case allows.

If you're talking about 4198 you won't need a magnum primer IMO. That is not a hard powder to ignite and the 300 Blackout is still only a 223 case so there isn't much room in there for the powder to shift and get lost. But in reality, if you're using a CCI #41 primer you are already using a Magnum strength primer so it's a moot case.

 

[fiftybmg]

For 300 Blackout, magnum primers will work better, as far as more consistent ignition and complete power burn are concerned.

Pressure differences in the case caused by different primers are a non-issue with that caliber.

 

[USSR]

Agree with ArchAngelCD, let the powder make/type determine whether a magnum primer is used, as well as the amount of powder used in a bottleneck rifle case.

Don

 

[plmitch]

Agree with ArchAngelCD, let the powder make/type determine whether a magnum primer is used, as well as the amount of powder used in a bottleneck rifle case.

Don

Thats a simple enough answer.

 

[jmr40]

It can get complicated. SOME standard rifle primers are hotter than SOME magnum primers. I know some guys claim better accuracy when using magnum primers in 308 target loads. I've experimented with the concept. If there was any difference in accuracy or velocity my skills, chronograph and rifles were not accurate enough to notice.

The only magnum rifle I own is a 300 WSM and none of my loads require more than about 65-66 gr of powder so I'm right on the edge of what is recommended. I have experimented with both standard and magnum primers and once again could not note any difference in either accuracy or velocity. I just stick with standard primers now to simplify things.

I use Winchester primers unless they are simply unavailable. They are supposedly one of the hotter standard primers too. Which may help explain why I don't note any difference.

 

[Schwing]

I don't think it is complicated at all. If the published data calls for a magnum primer, you use one. If it doesn't, you don't.

 

[Paddy]

Most data I see doesn't specify a primer at all

 

[NCsmitty]

If you choose to use a magnum primer with a listed start load, and work up to some point under the listed maximum load, you should be fine. A magnum primer will not be detrimental to your firearm if it's used within the parameters of the listed load range as I described.
It may or may not, be more accurate than a standard primer, but you won't know if you don't try it. Never substitute a magnum primer for an established standard primed load that is already maxed out. Drop the charge weight 3-5% if you do.

This is based on my experience over the 50+ years that I have been reloading. What you do with it is up to you.


NCsmitty

 

[W.E.G.]

As it pertains to SMALL RIFLE PRIMERS, the "standard" primers are thinner than the magnums.

I've used both.

The small ones usually fail (pierce) as the pressure is near the SAAMI max for 5.56.
This is because the standard primers are thinner than the magnums.

I've chronographed ammo fired with both types.
Velocity is the same.
Only difference is that the standards fail by piercing.

I've been loading 100% of my AR15 ammo with magnum primers for two decades.

 

[Paddy]

I like the explanations by all responders and especially ncsmitty and WEG because it makes sense to me in my imagination of the processes taking place. Thanks for that. I have a fear of hang fires and dreaded SEE and if magnum primers can help prevent these conditions then that's one plus for using them. In normal loads I will continue to use normal primers. Thanks again.

 

[OrangePwrx9]

I've seen some old data that recommended using magnum primers with Blue Dot in magnum revolver loads. That's a bad idea with today's Blue Dot. Can result in pressure spikes and pierced primers. I've run into it with 140 gr. .357 magnum loads. None of my more recent loading manuals recommend magnum primers with BD.

 

[Otto]

I concur with post 13.