When to use Magnum primers?

[MSU Marksman]

I'm wondering what the theory is behind Magnum primers and choosing when to use them? I've heard some guys switching to them for smaller rounds like a 6.5x47 Lapua with great result in accuracy, but I'm curious as to why this might be. Any thoughts?

 

[flashhole]

In general you want to use a magnum powder when you have a long powder column you want to ignite or if you have a powder that is difficult to ignite. Some will say it is better to have a magnum primer if you shoot in really cold climates, sort of like an insurance policy to guarantee ignition when you are sighted in on Buckzilla or any his Zilla cousins like elk and moose.

I use magnum primers on my 7mm Rem Mag, and 300 Win Mag (before I sold it). I've tried them on my 45-70 and 25-06 and could not distinguish a difference from conventional primers so stopped using them in those cartridges.

Not sure why you would get desirable results in a short case. I don't want my primer dislodging the bullet, I want the powder to do that job. In my 221 Fireball the milder primers give the best accuracy by a wide margin.

 

[Gene]

I have several competition rifles and have selected the primers with best accuracy, i.e. in the 6mmPPC, I use standard Federal 205; .223, its the CCI BR 4; 6mmBR, magnums seem better, so I use the CCI 450 or Wolf small rifle magnum. Also, 30BR, I use CCI BR4. In hunting rifles, I mostly use standard primers, but for cold weather hunts, I found the magnums ignite a little better. You have to test and compare primers.

 

[johnnyk]

A good case is one I ran across last weekend. I was loading the 70gn Ballistic Tip for my .243 using BLC(2). I selected the CCI BR2 and even though I was max or near max with the powder charge I was still getting the occasional hang fire. BLC(2) is a fine ball powder and a hotter flame, I feel, would eliminate this condition.
Cold weather could possibly be a reason to go to magnum primers but I think anytime you go over 60gns of powder it's beneficial to use a magnum primer. I remember reading the Fed215 was conceived for the Weatherby magnum rounds. JohnnyK.

 

[str8shoot]

I switched from a fed 215 magnum rifle to a winchester large rifle in my 7mag I gained a little accuracy and my ES improved quite a bit. I lost about 40fps velocity but I can use a little more powder if I want. It might be worth trying both, but if you are near max pressure back down a little if you go up to a magnum. I've meant to try the 215s in a couple smaller guns but haven't got around to it.

 

[Natty Bumpo]

The Speer reloading manual I have generally recommends magnum primers for spherical, or ball powder.