std vs mag primers

[nova71]

Is there any real advantage or disadvantage of using a std or mag primer ? I'm doing some reloading and am down to less than 300 std CCI200 primers but I have 4000+ of the CCI250 Mag primers and am thinking about subing the mag for the std. wondering if it would change POI much at 200yds.

[tacklebury]

Quite a difference.  Per CCI's description they are about 23% hotter and in some cases can significantly increase pressures.  I use magnums with hard to ignite powders like H-110 and I have heard some reduced load recipe's use them.  I'd be careful substituting them without research...

[shot1]

Sure you can sub a Mag primer for a standard primer IF YOU START ALL OVER WITH YOUR LOAD DEVELOPMENT. Mag primers will raise the pressure over most standard primers with the same powder load so just don't sub a mag for standard primer without backing off the powder and working back up. I have actually found that with some loads mag primers shoot more accurate than the load did with standard primers. I use CCI 250 mag primers with IMR 4350 in my most accurate load in my 25-06.

[Grumulkin]

Is there any real advantage or disadvantage of using a std or mag primer ? I'm doing some reloading and am down to less than 300 std CCI200 primers but I have 4000+ of the CCI250 Mag primers and am thinking about subing the mag for the std. wondering if it would change POI much at 200yds.

I doubt your POI would change but there could easily be a change in group size for the better or the worse.

I've interchanged various brands of large rifle and large rifle magnum primers over the years and in case the size of the 308 Winchester and larger, no adjustment in powder charge is needed unless you're on the ragged edge of high pressure where you shouldn't be anyway.  To get optimal accuracy, you may need to decrease the load a bit though.  In a 44 Remington Magnum load in which I tried large rifle magnum primers, I had to reduce the charge of H110 by about 1.5 grains but that is a much smaller case than a 308 Winchester case.

[Dand]

Grum may have some experience with his rifles but I ALWAYS back down a couple grains and work back up as a matter of safety. I mostly use the mag primers in my 300 win mag,  sometimes in my 06.

Somewhat depends on the exact cartridge you are loading and how close to max you are, also the type of powder.

Above all be safe.

[SHOOTALL]

And then there are Winchester primers that say on the box for standard and magnum loads  . Then don't forget benchrest primers that some say can be subed for either ( not sure I buy this one ). I have subed primers also and have had mixed results . Some loads the group either opened or closed others nothing. This has happened also with different lots (some years apart) of same brand. Others showed signs of pressure like bolts hard to open or split cases.
 I have since been very careful with switches .

[gypsyman]

Sierra manual states that you can substitute Mag primers for Std., just back your load back down to the start, and work it back up.
Talked with hunters that are in extreme cold, and a few of them use nothing but Mag primers, as they want to make sure they have enough flash.
Benchrest primers are not hotter than std primers. Just a more consistent flame. I've used them in several BR calibers. Not sure if you'll see much difference if you don't benchrest prep your brass.(uniform the primer pocket, and the flash hole)gypsyman

[Catfish]

Last summer I got a wild hair and did alot of compairing of primers. What I found totally supprised me. Most of the time there was no difference in velocity between mag. and standard primers and no signs of difference in presures. With some loads there was a noticeable difference in presure, but the supriseing part was that some load showed more signs of presure with standard primers than with mag. primers.  After finding this I would recomand you start down and work up every time you switch primers. It seemed that some powders did not care what primer was used and other powders changed their burn rate quite abit with different primers. I think that the real rule of thumb is that you don`t know untill you try it, so always start low.