Why would you use magnum primers?

CJS-6.5

Miss General Lee
Sep 15, 2017
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#1
For hunting dangerous game.
For super cold climate.
For capacity limited cases when you need more speed.

Anymore reasons?

I have tested regular primers vs magnum primers extensively in one of my 300 win mags and always have achieved lower es and sd and better accuracy. Plus it has a more progressive recoil. So for the average reloaded in North America that shoots targets and hunts...why would you. Or why do you use magnum primers?
 

phlegm

Sergeant of the Hide
Apr 3, 2014
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#2
I had an old-timer tell me that he used magnum primers when he knew he'd be in wet conditions. That may have been important once upon a time, but I've never had an issue.
 
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CJS-6.5

Miss General Lee
Sep 15, 2017
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#4
Yes. Where I live it gets to 40 below. With modern powders I have never had a problem running large rifle primers in magnum calibers. However if I was on a polar bear hunt I would use magnum primers. Don't really need .2 groups to take out a polar bear.
 

Festeraxp

Evil is Powerless, If the good are unafraid
Sep 23, 2018
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#6
If you use Winchester large pistol primers they only make one wlp. Says for standard or magnum on the box. I know pistols but 458 calls for them.
 

lash

Swamp Rat
Sep 28, 2012
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#7
I use Winchester magnum primers in my .338 LM, well, because, uhmm, it's a magnum with large case capacity?

Anyway, no data nor reason other than they actually work, for me. SDs at 3-5 using 285s and 7-8 using 255 solids.

Am I missing the point? Or what?
 
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ezekeial

New Hide Member
May 17, 2018
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#8
Am getting better accuracy with the ball powder am using in 308, and the CCI 34 is suitable for gas gun. And yes, there can be disadvantages to using ball powders.
 
Apr 9, 2006
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#10
This is what is making me think about trying some magnum primers. I'm currently running 41.5gr of H4350 in Hornady cases with WLR primers. At a recent match, the Labradar showed I was getting 2,710, with a SD of 13. That's pretty close to what he's showing with WLR primers, but by switching to WLR Magnum, his SD was cut about in half.

Unfortunately, I don't have a chrono for myself yet, but I'm tempted to try it out and see if the groups stay the same, or get better/worse at least.
 

Skookum

Entropy Personified
May 6, 2017
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#11
In my experience, changing primers is just another variable that has to be tried because the accuracy results are completely unpredictable.

However, when using ball powders in magnum cases, I think they (magnums) are the only prudent option.
 
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Strykervet

Resident Phoenix Eye and Dim Mak Instructor
Jun 5, 2011
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#12
All the CCI military primers are a magnum mix they say, so I'm supposing that has to do with reliability of ignition. This is all I use in rifles at the moment and I gotta admit they all go bang and I get good ignition evidenced by little to no unburned powder residue.

You also use magnum primers in large capacity cases to ensure complete ignition of the powder sooner than later. .50 Beowulf is an example that uses large magnum pistol primers.

And then some loads in the manual just call for magnum primers because I'm assuming that during testing, they found better results using them. The books generally say you can use the magnum primers if you reduce the load another 10% or even 20% because they do increase pressure and faster, regardless.
 

CJS-6.5

Miss General Lee
Sep 15, 2017
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#13
I appreciate everyone's contributions. I was reasoning in my reloading room that a competent reloader, with access to the most modern powders, with every necessary tool to build a successful long range load, has no reason to use magnum primers until the charge is 90 grains or larger or the powder charge is unusually long due to an inefficient case. When pushing a heavy for caliber bullet a precisely delayed charge propulsion can be very effective. And not only for accuracy. Recoil and barrel life should also benefit.
 

CJS-6.5

Miss General Lee
Sep 15, 2017
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#14
I know from experience in shooting several of my magnum cartridges at the same velocity, braked and unbraked that the magnum primers definitely have a faster recoil hit then regular large primers. I would like to have others experiment and share their findings to make sure my findings are not false or just restricted to my scenario.
 
Sep 27, 2008
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#15
Recently tried Alliant 2000 MR in my 308 GAP 10. Shot some 168 AMAX W/ 47.0 grains and 178 AMAX W/ 45.0 grains. I used CCI #34's. Both loads shot very well & I got decent velocity W/ a 22" barrel. 2740 FPS AVG W/ the 168's and 2611 FPS AVG W/ the 178's.

Brass looked good, I could probably go another grain or two if I wanted to.
 

stalwart300

Sergeant of the Hide
Apr 14, 2018
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#16
Different powders in different calibers in different guns like different loads. For my 6 creedmoor 107 smk lapua brass has best velocity left sd's using cci small rifle magnum primers. My 308 loves non magnum large rifle primers. Find out what it loves to eat.
 
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stalwart300

Sergeant of the Hide
Apr 14, 2018
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#18
Im not sure besides better consistency (my guess). I have bench primers, regular rifle and magnum for my creedmoor with the powder etc that I chose magnum send to give me the best consistency.
 
May 20, 2006
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#23
I'm late to the party here, and am by no means a Primerologist,,,, but I was always understanding that "magnum" primers had thicker/stronger cups, to deal with the chamber pressures. That's what was learned to me, many many decades ago by "my elders" back then.

I cannot substantiate that in any way,,,, as it could very well be an "old-wives-tale". It could also be a 'carved-in-granite' law of physics, for all I know.
 

308pirate

Gunny Sergeant
Apr 25, 2017
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#27
I had an old-timer tell me that he used magnum primers when he knew he'd be in wet conditions. That may have been important once upon a time, but I've never had an issue.
A lot of old timers operate on BS that gets repeated with no evidence.
 

Holland375

New Hide Member
Oct 25, 2018
21
6
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#28
A lot of old timers operate on BS that gets repeated with no evidence.
In my experience, changing primers is just another variable that has to be tried because the accuracy results are completely unpredictable.

However, when using ball powders in magnum cases, I think they (magnums) are the only prudent option.
I agree 100 %
You do need magnum primers with big case capacity, even more so if using ball powders and some specific big handgun cases like 357, 41, 44 and powders like 296. The cci 450 have been used a lot in benchrest because it gives them the smallest groups abd the added benefit of harder cup. They run hot hot loads. On the benchrest primer publication there is an old article on primers but it is old, so by now most manufacturers have probably changed but it gives you an idea of the better performers and why.
So there is a specific aplication for magnum primers but it gives you more flexibility to experiment in the accuracy department too.
 

Culpeper

One divided by F
Nov 25, 2006
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#29
Working up a compressed load and noticing the telltale sound of firing pin strike, quick puase, then detonation. Also, the opposite with very light loads. With compressed loads back of 5% on the initial load.