Changing Primers? Will Cause Pressure Diff?

[Huntsalotey]

I am wanting to start loading my loads with Magnum primers rather than LR primers. I am loading for a 7mm-08. Can I keep my same loads and make the primer change without it affecting pressure? If it does about how much more pressure would one get from this change. or should I say, How much would I have to reduce my powder charge in grains to be safe making the primer change to Magnums. Thanks

[Danny45]

This probably should go on the "reloading" board so if it disappears, look there for it.

Any time you change a component, you "can" see a difference. Case thickness, hotter primers (like Magnums), ball powder to extruded, etc can all effect a number of things, including pressures. Not many people can predict what will happen unless they've made the exact change that you're talking about. Even then, chamber tolerances (lack of consistency) can eliminate even that.

Whenever you make a change in your components, start from scratch and work your way back up. That's the only safe way to do it.

[herman]

The only time I used mag primers in my 7/08 is when I am using ball powders like w760,They really aren't needed but they are dirty powders and the mag primers help them to burn a little cleaner. I would go down at least 1/2 grain and work back up.

[GordonGekko]

Well, I'm by no means an expert metallic cartridge reloader (and don't need to be since I have a buddy that is), but I load a lot of shotshells and changing primers (even between brands) can cause pressure changes as for how much, I'm not sure. I know that the magnum primers will burn hotter or longer than regular primers (and sometimes both), and are intended for large capacity cartridge's or hard to ignite powders. I suppose if I was going switch to magnum primers (or any other I didn't have a recipe for) I'd start with the lightest loads and work up from there, carefully looking for pressure signs. Just my 2 cents, hope it helps.

Gordon

[Vapodog]

I now use magnum primers in all my cases the size of .257 Roberts and bigger. I always backed off about three grains and worked back watching for pressure signs.....in all cases I worked back to the original load.

My own personal experiences are that there's no difference between LR primers and magnums.....BUT DON'T YOU BELIEVE IT...always back off the charge and work back. It's just smart behavior to get used to.

[cherokee_outfitters]

Changing primers can make a difference on pressure. If you put a large rifle primer in a magnum case that suggests a magnum primer, then you have to back off the load alittle. Because the lr primer will burn the powder slower and you will have more pressure in the chamber. This can be a bonus for more uniform powder burn but it causes pressure and it needs to be handled with more caution. I'd say stay with whats recommend on rifles.

Pistols need all the powder burn they can get. It is okay as long as your not swelling cases. But I've learned that pistols tend to like loads that are not hot.

Changing primers will cause a pressure change, but very small amount from what i have seen. I also tryed this with my 308Win. Unfortuately I get more accurate results out of Fed 210 than a 215. It seems not the hottest primer will produce the most consistent ignition. I know that is not always true, and I don't have any data to push that way besides my own experience.

[ColoradoElk]

Danny & GG said it very well. Things do change. In speaking with folks that measure chamber pressures, they said changing the primer can impact pressures as much as 1.5 grs +/- of powder, which is enormous. Another thing to consider is ambient temp when shooting. You could develop some loads in the winter/spring and end up with a face full of action in the summer...

You have to start over.

Be careful.

CE