/I'm probably going to open a can of worms here but here it goes. If I took an identical load one with a regular primer one with a magnum primer what difference if any will I observe?

Example:

Ruger 204, berger 40 gr BT, 26gr Varget, CCI Primer
Ruger 204, berger 40 gr BT, 26gr Varget, CCI magnum Primer

Would I see any difference in FPS or group between these two loads?

What if the load was a partially compressed load, would there be a differance then?

I'm just trying to figure out what a magnum primer does that a regular primer doesn't do.

Thanks

Dave

It is one of the great things about reloading you can try it and see. Magnum primers are usually for larger amounts of slower powders but the increased briscillance of the magnum primer can improve ignition in normal loads... or.. it can rasie the pressure and increase the SD and ES of a load.. or.. it can have no effect at all.

Run 10 of each over the chrono and measure the groups and see what you get.

Very true Dawgdad. I remember when I first started handloading for pistol about a hundred or so years ago (it certainly seems like that) one of the things that was all but pounded into my head by the guy teaching me to load is that magnum primers can be the equivalent of up to an extra grain of powder.

As DD says Dave...try it mate, but not with a maximum load, and if you are going to try a compressed load, ensure that it is a load from an accredited Handloading Manual. Don't want to see an obituary posted here mate.

Cheers, Vince

In my 300 Whisper, magnum primers gave consistently lower MV than standard primers.
I am sure I have checked and double checked my primers, I have also purchased a fresh box from another supplier just to try.

It must be because of the low charge amount.

What's the RECIPE call for?

204's a pretty damn zippy round. Doubt I'd wanna do anything to alter the presure curve on that. Esp on a "partially compressed" load (what the heck is that?), as if it comes out of compression during settling during transport you now have a BOMB. I avoid compressed loads like the plague. Way too risky and inconsistent. If you need more room find a powder with the same speed and and a lower VD.

If the recipe calls for a mag primer, use it, with a START load, go from there. Varget's a medium speed powder and @ 40gr ya dont even need a mag primer.

Start loading long colums of 68gr+ of 4831 or slower? Then you can use a mag primer IF the recipe says too. Mag primers are wild cards. They can alter pressure curves and send things over the top faster than the chamber can handle them. It's dont take muhc @ 50-60k PSI.

My only experience is with loading regular versus magnum is for the 308. Using 43.5 grains of Varget and a 168 grain bullet the magnum primers gave me a higher average velocity and a lower deviation. I will check my records this PM when I get off work to get the exact numbers. Their was a slight improvement in grouping but I can't say it was the primers. This is a medium load and not compressed.

Added: CCI 200 versus CCI 250

The primary idea behind magnum primers is to provide a hotter ignition for larger amounts of powder. Cold climates can also benefit from the use of a mag primer.

With that said.......... they are like any other component that can be substituted and experimented with !!!


Just remember......... they are not universal......they can not be interchanged freely !!!
They vary in strength from one manufacturer to another.
It's possible that ones standard is just as hot as an others mag.

Personally I've never seen the need to use them when not called for, but others have found them to be beneficial.

gelandangan wrote:

In my 300 Whisper, magnum primers gave consistently lower MV than standard primers.

Were they the same manufacture or different brands ???

magnum versus regular...
and what about match primers?

I think bench-rest and match primers are closer to magnum primers, plus they are suppose to be more consistent in the cup paste mixture.

Geland:
When you tried those magnum primers, were they on the same day as you tried the standard primers? Weather has a lot to do with overall performance.

Aloysius wrote:

magnum versus regular... and what about match primers?

Funny thing you should mention that Aloysius.I was after the last little bit of accuracy and tried those cci benchrest primers in my 223,wow-what a waste of money!I had been using cci magnums and winchester std primers and getting really good accuracy,and tried the benchrest primers-blew my groups,and on the chrony-the deviation was 100 to 200 fps!!!!!!!!!!!!!Now this was only with H4895 powder,and I never tried them with another type of powder,or bullet weight.But why change powders when I get consistant 3/4 to 3/8 inch c to c groups? So why do they call them bench rest primers?

Cuz you use them in connection with BR reloading recipes and methods and components. For standard target and hunting loads dont even bother. Just buy standard, easy to find primers and get back on with life.

Checked my records

Bullet: 168 Grain Hornady A-Max
43.5 Grains Varget
O.A.L. 2.800
New Winchester brass full length sized.
Range was 50 meters.

5 shots each

CCI 200 LR = Avg 2468 FPS Spread 2437-2506 Avg Group .44 **
CCI 250 LR = Avg 2536 FPS Spread 2520-2554 Avg Group .31

** I dropped two bad shots for grouping as I definitely pulled them. The guy next to me was firing some magnum "shoulder cannon" and my timing was off with respect to trigger let off. Trigger was dialed down to just over 1 pound. With these included Avg. Group was .91.

Both shot the same afternoon, same rifle over the same chronograph placed at the same location. The barrel was fouled and warm for each shot string.

My rifle is 1 in 12 with a 22" barrel. My theory is that the magnum primer gets the bullet moving faster which optimizes the potential of the shorter barrel as less propulsive power is lost to muzzle blast. It would be interesting to repeat this with 24-26 inch barrels to compare the FPS increase, if any, the magnum primer provides. On the safety side, if my theory is correct, this translates into a higher peak pressure and a reason not to try this with a maximum or near maximum load. Maximum for this bullet/powder combination is 46.0 grains (Hodgdon reloading site).

Hey MacD
I use magum primers in both my 22-250 and 308 loads WHEN I am hunting in 0 degree F or below weather. I have found that using the magum primers in warm weather throws my accuracy right out the window. And as I am in brisk old Saskatchewan, I have had plenty of experience with the benefits of mag primers.

I did winter survival training 40 miles east of Churchill Manitoba in March. I made the mistake of grabbing my 7.62 mag in my outside pocket with my finger tip open gloves and it stuck to my fingers. It was so cold it felt like a burn. Those Valcartier Industries rounds fired every time but the FN's sometimes just froze after a few mags. Now from what I have heard Manitoba is tropical compared to Saskatchewan.