Using magnum primers

Had a random thought (a brian fart if you will) about magnum primers…

As always, working the load up is the go, but out of curiosity and in my case it would be Magnum Primers for Large Rifle, what’s the powder equivalent or even if there such thing.

For example, baselining a given charge of X grains of powder for some bullet, etc. using LR primer… Swapping the LR primer for Magnum Primer, is it equivalent to say 0.2 grains of powder, 0.5 grains? Can such relationship be made? Etc.


No, no such relationship can be made as there are too many variables. Changing primers can alter the pressure significantly from a known load. and the accepted wisdom is to reduce your load by 5% and work up again. A study by an Internal Ballistics expert some time ago found most primer changes only altered a load by about 5% anyway, but if you were on max pressure with a given load changing primers could push you over. Several Internal Ballistics studies can be found online and are worth a read, Cheers

From what I have been told when using ADI powders you should see very little difference as the powders are so easy to ignite. There is a scientific word for it but I forgot. Big difference when using other powders. Too the point that even in magnum size rounds magnum primers are not needed when using ADI powder.

Okie, thanks all.

Side note, @sungazer, yup I do use ADI powders pretty much exclusively.