Differences in primers brand on a load

[WVELK]

I have never experimented too much with different brands when developing a load. Two questions: how much of a difference have you seen one primer make over another with the same load; and why does that happen?

 

[Pharmseller]

Primer brisance (hotness) affects ignition. Ignition affects pressure. Pressure affects velocity. Velocity affects precision.

I’ve seen a little difference between primers using the same recipe but not much.





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[Harvey_NW]

Usually just a difference in velocity, never saw a discernable difference in dispersion in the limited testing I've done. I usually just pick a primer suited for the case and roll on. For a long time it was whatever I was able to acquire.

 

[Vern400]

Primers affect the speed at which the powder column is ignited, and if you'll let me use an engineering term, the rate of pressure rise. That in turn will impact velocity and possibly barrel harmonics somewhat.

Are primers completely interchangeable? No.
Can you get a number of different primers to work well with a given load? Probably so.
Will you have to tweak the charge? It's likely if you're on a node and you'd like to stay there.
Will it change the way the load behaves? Probably.
But except in extremely rare cases, it won't change 3 inch groups into 1-in groups.

There are some corner conditions, like using light primers with Magnum powders that are exceptions to these general ideas. Another is using a small rifle primers in larger capacity cases at extreme low temperatures. But I think your question was more general than that.

That being said.... If you're precision shooting, sometimes it's useful to test several primers. In theory, low ES indicates that your case capacity, powder, primer, and bullet weight are working well together. One primer type May shine out better than the rest.

 

[TaperPin]

I have never experimented too much with different brands when developing a load. Two questions: how much of a difference have you seen one primer make over another with the same load; and why does that happen?

As others have said it’s mainly a minor velocity and maybe standard deviation thing, but not all primer cups are the same hardness. A fairly fast load developed with CCI primers may be too spicy for a primer with a softer cup.