Can you substitute magnum primers for regular primers?

[bigjeepman]

I am in pretty good shape as far as primers go but I have a question for you. I have been reloading for many years but have always gone by the book ... never going over listed max loads as I have always seemed to find that sweet spot before I got there. So I am guessing almost all of my loads for .38 spl, .357 mag, .45 acp, .45 colt, 7mm-08, .308, and .444 Marlin for examples are in the range of 85% to 90% of max loads. My 45/70 loads for my Marlin 1895GS and my Sharps rifle are only 1200-1400 fps so those are not even close.

Here is the question ... can I use (if I have to at some point in the future) substitute magnum primers for regular primers and not have problems? Another example ... shooting a Sierra 168gr HPBT over 44.0gr of Varget in my 10FP rifle? Another example ... shooting a Nosler Accubond 140gr over 41.6gr of Varget in my Tikka T3?

The reason I ask is because about 25% of my primer stock are magnum primers. It will take some doing to get down to that but it could happen as the future is fairly uncertain about availability with reloading supplies. I am thinking I might have to back off a grain or two of powder but I am uncertain if it is necessary.

What do you think?

[celltech]

I have seen reloading data that suggests a magnum rifle primer raises the initial pressure by ~1600 psi. That would equate to ~.4 grains of powder in something like a 6.5 Creed load...so not a giant difference.

[Robinhood]

Short answer, yes. A small reduction in charge weight is suggested as Celltech stated.

[Stumpkiller]

Agree with above. But I don't know the powder reduction you'd need. I'd drop back 5%. That's the "safe" minimum whenever you change a component . . . that in practice I'd wager few of us practice.

[bigjeepman]

What I am understanding is that if I ever have to use magnum primers that did not call for it, start load development over again by reducing powder charge and work my way back up. Hodgdon's load data for the .308 Win 168gr bullet and Varget powder ... minimum 41.0gr ... maximum 45.0gr. So at my 44.0gr load, I would be "probably" be okay but would be very wise to back off to say 43.0gr and move forward slowly in say .2gr increments.

This makes a lot of sense now.

[stanekjm]

Back a few years ago when we had a similar crunch on everything related to guns/ammo/reloading, I came across a small lot of magnum small pistol primers. I reloaded a few hundred 115 and 124 gr 9mm cartridges with them. Never saw any pressure signs. Granted I was staying at the minimum according to my Speer manual (which tends to be a little more liberal) If they are all you can find, use em and like the others have said, reduce your max charge and watch for flat primers or if you are really over pressure cratered or pierced primers.