Magnum rifle primers for .308

**Dr.Steel** · January 22nd, 2021, 07:26 AM

So we are all aware of the shortages. And I was a little late on hoarding reloading supplies like large rifle primers. But I have plenty of magnum rifle primers.

So my question is can I run magnum rifle primers for 308 if I dial back my powder? I have searched on the web for answers but have yielded mixed opinions. If anyone already has a good recipe consisting of magnum primers, varget powder and 168 Sierra match kings, they would be greatly appreciated. Thanks

**57springer** · January 22nd, 2021, 02:21 PM

Reduce the powder by about 5% , I use Mag primers in my ruger m77 308 . No pressure problems .

**Bang** · January 22nd, 2021, 03:40 PM

This professional loader measured pressures and velocities on 9mm using small pistol, magnum pistol, and small rifle primers.

The differences are close to none. Why not similar results in rifle cartridges?

Video: https://youtu.be/NGVRGsoOr6k

**knight0334** · January 22nd, 2021, 03:46 PM

Yes. As mentioned by the fine gentlemen above, you may need to decrease power charge.

Some powders are more sensitive to hotter primers than other powders.

Same holds true for any type of cartridge, or caliber of cartridges.

Good practice is to load a few at reduced charges, test fire for velocity differences versus normal charge and primer, and look for pressure signs on casing. If all look good, you may work your loads back up some.

You may find that the mag primer offsets the reduced charge resulting in same velocity and overall ballistics. ...thus saving a few grains of powder.

**HanzMcFeely** · January 22nd, 2021, 04:21 PM

I’m curious on this also...from what I’ve been reading and what was said when I asked the same question re: 270win the general consensus is that you need to cut your powder charge back with magnum primers as they can cause pressure spikes.

Lemme ask this though to further confuse things:

Doing some research into reloading 308 it was said that using IMR4831 is not the best option since it’s such a slow burning powder. What about using the magnum primers to offset the difference then?

**Delkal** · January 22nd, 2021, 07:39 PM

On paper magnum primers are supposed to be "hotter" but its not going to turn a safe load into a grenade.. The myth that you will blow up if you start using them started with the reloading companies wanting to sell you more components then turned into a lawyer/ liability issue. There are a number of other variables (rifles throat, cartridge OAL) that has the potential to increase pressure way more than substituting just a primer a primer. Yes it is true if you have load that is ALREADY overpressure for you firearm and then substitute anything hotter there may be a problem. But today's reloading manuals are so conservative they are a joke (and you will NEVER get their spec velocity). Adding a mag primer wont get you there either.

**abner13** · January 22nd, 2021, 07:58 PM

I always use LR magnum primers in any military cartridge , especially when using ball powders. Have been for probably 40yrs. Hodgdon used to recommend them with many lots of BLc-2 and 7.62x51 loads. I even used them for 30-40 Krag loads with IMR-4350. It's not so much as they are all that hotter , but the cups are also harder and don't flow , or blow , especially in semi-auto military rifles. True CCI mil-spec primers are not always easy to find. LRM primers were always the go-to option.