Magnum Primers...is my thinking correct ?

[JonB_in_Glencoe]

after reading the thread on Winchester primers, I thought I'd start a new thread requesting input on Magnum primer usage.

My understanding of use of Magnum primers are for one of the three following conditions.

1. shooting in extreme cold conditions

2. loading Tall and Large size cases (ie belted magnums and larger)

3. loading very light loads. (where the powder occupies less than 50% of the space available, examples would be some 38spl loads, 45LC loads or some rifle "gallery" loads)

Disclaimer: always take all the precautions of working up a load using the prescribed instructions in a respected reloading manual.

[Rocky Raab]

Jon, I've never subscribed to the idea of using mag primers in very light loads. The logic escapes me.

But I'll add one other condition as a substitute: When using certain very hard to ignite spherical powders, such as W296/H110 or H380.

[felix]

Number three is very incorrect. Use filler, or use a powder easier to ignite, perhaps both. ... felix

[JonB_in_Glencoe]

Rocky,
the logic of using a mag primer in a light loads is about the position of the powder in the case. If the gun is tipped downward right before firing, the powder could flow away from the primer, making it more difficult to ignite. Now a primer that provides a longer and hotter flame should overcome that difficulty more so than a standard primer.

whether it's correct or not, I can only assume.

[grouch]

I've tried it several times over the last 50 yrs with cartridges up to 30 - 06, mostly with light loads. Magnum primers have not EVER helped - they've always been worse.
Grouch

[Rocky Raab]

Jon, while it has been shown that powder position can indeed have an effect on pressure and velocity, it is doubtful that it has any effect in real life. To show the effect, one has to deliberately tip the gun and then carefully raise it so as not to re-distribute the powder.

In real life, the gun is held more or less horizontal (I have yet to aim at my own boot with one), and the action operated between shots. Both these things tend to jostle the powder evenly along the case. Then there's what I call the "leafblower effect" of the primer going off. That stirs everything into a perfect maelstrom inside the case.

Try this: prime a case. Put a small pile of powder on your sidewalk. Now place the gun muzzle an inch from the pile and fire the primer. Even inches away from the primer (the whole length of the barrel) that pile of powder simply disappears. If it stirs powder that much from so far away, it must do so even more thoroughly inside the cartridge.

[fredj338]

I only use mag primers w/ large amounts of ball powder. Even in magnum rifle cases. Unless the powder volumn is over 70gr, it gets a std primer. The only handgun loads that get them are H110/W296 in any of the magnums.

[geargnasher]

I only use Magnum primers if a standard primer fails to supply consistent ignition. IME it IS necessary to use magnum with 296 in the .44, otherwise it simply won't light.

One of the things I've noticed about SOME reloading books, especially those put out by or affiliated with companies that also make primers, like Speer, is that magnum primers are often listed where they are unnecessary: Gotta sell mag primers, too, right?

Gear

[felix]

It's the length of the cartridge, not the amount of powder per se. I would still start with mild primers with the wide-bodied 70 grain cases. ... felix

[mpmarty]

Heck I even use LP primers in 45/70 loads and they work just fine. I don't use Magnum primers at all as I don't use 296 or H110. My H380 loads in 22/250 light off just fine with standard primers but there we are talking about a relatively small case. My 7mm Remington Magnum burns H870 just fine with standard LR primers too.

[jonblack]

My usage of small pistol magnum primers is a bit unorthodox. I use them because I have them. Several years ago I bought about 15k at a great price. Since then I have worked up 9mm loads and 380 Auto loads. I am also about to work up a .40 S&W load. Over at the Brian Enos forum, many shooters use them in this manner.

As a side note, I should explain that all of my loads are "plinking" loads. I do not load max loads. As long as the load cycles the gun and hits the steel I am shooting at, it is fine for my needs. In the SD role I use factory ammunition.

jonblack

[jmsj]

Before the "Big primer shortage" I used Winchester LP primers in all my large pistol primer cartridges, cast and jacketed. For cost and convenience it was easier to stock one primer. It seemed like they were the first to disapear when primers became scarce. Last week I was able to buy 2000 of them locally for the first time in long time.
My most accurate load in my Ruger Bisley Vaquero .45 Colt uses Winchester large pistol primers, a 255gr RNFP and 2400 powder. They seem to work well in my .45acp and .44 magnums as well.
I have not done the extensive testing that others here have, I wish I had the time to. But for now I'm glad to be able to get them again.
jmsj

[lwknight]

It is commonly excepted that Standard LP primers in 44 mag with 2400 is just fine.
If you only have magnum primers then reduce the load some.
I cannot say what percentage to reduce the load because every powder is unique.

[sagacious]

If one uses the WLP primer, one need not worry about when to use a magnum primer.
Simple and effective.

[44man]

Let's see, when did H110 and 296 first come out? Can't remember but my .44's and .45's have never seen a mag primer with either powder except for testing.
They triple groups, plain and simple, even WLP will open groups.
It is entirely not true that a .44 needs a mag primer for ANY powder.
Even the .475, .454 with .460 brass, the .460 and up will all ignite with a standard LP primer but the larger cases are more accurate with mag primers.

[Bass Ackward]

I use magnum primers for light loads and pistol primers for full case, low pressure situations. Same logic as Jon uses. Cause I hate filler other than powder.

Every load gets the safety test. And if it shows powder position sensitivity at any season of the year, (cold is usually the worst) it is reworked with a magnum primer.

Why? Because it's not the strength of the average primer in the box. It's the strength of the weakest one in cold weather that causes problems.

But in truth, I don't load many "light" loads for rifles any more. Handguns either. If I need a lighter load, I use a case design safer for this purpose.

[abcollector]

44man,

Just trying to understand what you spoke of- are you saying that you don't use LPM primers for powders like H110/296? And don't like using Win LP primers for these powders also because in both cases, they open up the size of groups? Cast or jacketed are treated the same? Do you use a heavy crimp? In your experience, would this apply to the .357 mag as well?

I'm just trying to understand this thing about always use Magnum primers with powders like H110/296.

Thanks Sir.

[Whitespider]

...Then there's what I call the "leafblower effect" of the primer going off. That stirs everything into a perfect maelstrom inside the case...

I'm not so sure I buy that one Rocky. If there's enough powder in the case that some of it is in front of the flash hole, then yes we would have some stirring. But if the powder charge is small enough to put the level below the flash hole, I don't think so, or at least not enough to be described as a "perfect maelstrom"; It would be more like a flutter of just a few of the grains resting the surface of the charge.

It's sort of a physics thing; pressurizing something doesn't usually stir up the contents, but the rapid release of pressure will. I have a little one-gallon yard sprayer, made of translucent polystyrene; ya' know with the hand pump on the top. Well, I installed a tire valve in the top so I can quickly pressurize it with an air compressor. If I fill it to a level below the tire valve and hit it with compressed air the surface of the contents barely gets a ripple on it. But, if I leave the top lid off, and than hit it with compressed air, I get soaked by the contents as the pressure flows out the top.

You also have to consider the "time" factor. As the pressure flows into the case the "flow" has to flow long enough to overcome the inertia of the "at rest" powder grains. But as the pressure builds inside a sealed container the speed of the "flow" is rapidly reduced; the smaller the container, the less "time" the "flow" has to act on the contents.

Try this experiment. Take a 2-litter soda bottle (representing the cartridge case) and install a tire valve in the bottom (representing the flash hole). Now put some sugar (representing gunpowder) in the bottle so that when you lay the bottle on its side the sugar is well below the tire valve. Screw the lid on tight and hit the tire valve with compressed air (representing primer ignition) for a split second so you don't split the bottle. You will notice that very little, if any, of the sugar grains are disturbed. OK, now repeat the experiment but this time replace the screw-on lid with a tight fitting cork (representing the bullet), try and get as tight a fit as possible. Now hit the tire valve with compressed air and watch the sugar as you do; only when the cork blows out does the "perfect maelstrom" happen, probably carrying a large amount of the sugar out the mouth of the bottle.

Now if you apply this to a cartridge... Normally the powder has ignited long before (relatively) the bullet leaves the case. The "perfect maelstrom" doesn't happen until after the bullet is well on its way down the barrel because it would need to accelerate to a point where pressure is rapidly flowing out of the cartridge case.

[felix]

Rocky is right on, Whitespider! Primers are shocking devices. ... felix

[Rocky Raab]

The gas jet from the flashhole is indeed a powerful blast of high-speed, incandescent gas and particles, not a "spark" as some folks envision.

Nonetheless, since my last post yesterday, I have been re-thinking the issue of magnum primers with small charges in large cases, and I am forced to make a small retraction or concession. I know that in small cases, a too-hot primer can and does unseat the bullet before the powder can ignite (most obvious in the Hornet). That causes a great deal of pressure/velocity variation and lost accuracy. That being the case (pun intentional) it should also be true that in a larger volume, a mild primer may not develop enough heat or pressure to properly ignite even a small powder charge. A certain amount of pre-pressure is required - possibly as much as 10,000 psi - before powder can ignite properly.

So, I'll concede that in some instances, a magnum primer may provide improved ballistic consistency even with small charges. The logic no longer escapes me - not completely, at least.