Using magnum in lieu of standard primers

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ciwsguy

New member
So with the primer shortage, sometimes one has to use what one can get. So I’m building some supplies to reload 243 Winchester using Hornady ELD-X bullets and IMR 4064 powder, the issue I have is load recipes cite standard LR primers and I only have magnum LR available. So since magnum primers are hotter than standard primers, should I just use the magnum primers and reduce the powder charge to minimum?
Looking for opinions from those more experienced than me.
 
This is very much a "your mileage may vary" type situation. But yes, you SHOULD be able to safely basically start over with load development, maybe dropping another half grain below what the book says.

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when you change ANY component from the listed data to something else, you drop back to start level loads (or slightly below unless specifically advised not to by the powder maker) and start over. Once you have established things are still safe at start load levels, work up in the approved step by step manner.

Do NOT substitute magnum or standard large rifle for large pistol primers. Small rifle and pistol primers are the same size, large ones are not. (diameter is the same, height is not)
 
The biggest change I've ever seen a primer make was equivalent to a five percent increase in powder charge. Usually it is less, especially with large primers for some reason, but never assume. Always drop the charge at least that much for a primer change, then check how the velocity compares to the previous primer and adjust accordingly.
 
Using a 260 Remington, 26 inch barrel , 120 SMK's, 36.2 gns Varget, Peterson cases with small primer pockets when going from CCI 400's to CCI 450's velocity increased from a average of 2627 FPS to 2645 FPS. These were 10 round groups.

Oddly enough when using Lapua cases with large primer pockets it took 37.7 grains to achieve the same velocity.

Like the above posters said when making any major change to a load it is prudent to do a low round count pressure test starting low and working your way up.
 
I tend to use magnum primers if the temperature gets really cold.

On a 19 deg day in Northern VA several years ago, my chronograph recorded an average increase of 12 fps in my .270 Winchester M70 when using magnum primers with an otherwise exact load using LRPs (same brand of primers). That 12 fps increase is equivalent to adding about 0.2 grains of powder.
 
I have done this with small pistol and small rifle primers, but never large. I would not have a problem doing it, but you woukd need to work up from start.
 
I have done the substitute a few times. I just drop 3/10 off the load.

As my loads are not at max, that seems sufficient and I have had no issues (and technically, you are supposed to drop down more). There may be powders that act wildly different but none I have seen.

I am currently playing with H4831 30-06 loads and colder temps (15-35) and am seeing some interesting results. The Mag Primers loads have been more accurate but are also wilder ES and SD wise. While the 6.5 Lapua will show an odd flyer on a good called shot with a 40 FPS variation, the 06 does not seem to care.
 
That would usually be OK, but keep in mind that 3/10 of a grain is a much more significant percentage of a small cartridge load than a large cartridge load. For that reason, I gave 5%, which came from a 223 load performance reported by Charles Petty to give 3300 fps with a particular magnum primer and 3150 with the mildest standard primer he used. The actual number was something like 4.6% of the RL 10X load he used, but I rounded. And it is unusual. Most of the time, the difference is no more than 10s of feet per second, where a fraction of a grain will cover it.
 
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