Large Rifle Magnum Primer vs Large Rifle Primer

It sort of depends on the magnum primer; some magnums compare to a standard Win LR. In a general sort of way, a magnum primer sort of compares to a extra grain of powder as far as pressure goes. Not the first grain, but the last one.
 
Yes, if using large rifle and switch to magnum, start at a lower powder charge. I tested it, and actually ended up increasing the powder charge when swapping to large rifle after pressuring out with magnum primers.
 
Haven't tried regular large rifle primers in my .270 load, have used Winchester lrmp as suggested in a recipe I found with H4831 SC, and found a great little node. With this shortage, may have to go to lrp and see if there's a big difference.
 
I only use CCI250 magnum large rifle primers in all of my hand loads.

It makes for consistent pressures at all temps and I start my loads right at mean in the manuals, then work up from there.

I load three cartridges to check for visible pressure signs.

One at mean, one in the middle between mean and max and one with one grain less than maximum.

When I see the results, I use the hottest load that doesn't show flattened primers as a starting point for accuracy, sometimes the load has to be decreased.

Accuracy is far more important than velocity.

I also work up loads on cases that have been fireformed to the chamber of the intended rifle the loads will be used in and partially neck resized only.

This helps to keep things manageable and eliminate another source for surprises. If you're shooting a pump or semi auto rifle, then you should be resizing accordingly.
 
Gerald said:
How does the pressure compare in a load with all things being equal except said primers?
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All things are NOT equal.... some powders do not burn linearly with an increase in pressure... and the Magnum primer should be put more energy into the kaboom.

The easiest answer is go back to starting load and work up... WAY too many variables to make a simple assumption.

Be safe.

Jerry
 
I've compared CCI 200 vs CCI 250 and the differences are slim, in temps down to -16c

Tested in 3 cartridges, with 6 different powders each

CCI 200 large rifle gave good ignition in cold temps, even in a 7mm Rem Mag
 
Believe the magnums were developed for the long/large powder charges in some of Roy Weatherby's original 1940-50 calibers.

I use two cut offs to decide if I use a mag primer. Seems silly, but if the headstamp says magnum, and if powder charge is greater than a max charge 30-06 family about 60 gr.

Reloading is such a rabbit hole. You can get anal in every component, every case prep step, add case prep steps....etc etc.
I'm not a target shooter, I shoot and hunt. My personal ethical cut off is 300 yards; therefore, my MO is sub moa in a good hunting bullet......load 10 yrs worth. Often I'm a long time revisiting that caliber/firearm.
 
nowarningshot said:
Believe the magnums were developed for the long/large powder charges in some of Roy Weatherby's original 1940-50 calibers.
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The Federal 215 was developed for the .378 Weatherby. There's actually a Federal 216 that is made for the big case lower pressure Nitro Expresses, but they were never released to handloaders as far as I know.

There was test published in the National Rifleman years ago called "effects of component switching in the 30-06" or something like that. Using pressure testing equipment they swapped primers and bullets, maybe cases too but I can't remember. Just on the primers they were able to change the pressure by 10,000 PSI in some instances, had no change in others and interestingly sometimes the big pressure changes didn't come with a change in velocity.
 
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