Bench rest primers?

[Matt Anthony]

I use cci primers all the time and I do not waste any time to work up a load when I change to federal or winchester primers. I talked about primers with a rep from Federal, and the story he gave me was that they mark primers as match primers because they look at them a little closer for quality, not the strenth of the primer firing.

All primers, be it regular, match or magnum do have differences, I have chronographed many combinations over the years and witnessed those differences.
When changing primer brands and even lot numbers of the same brand, there will be differences due to mixture content of components and the components themselves.
Industrial standards dictate to work up the load when changing any component from a developed load, that's what the manufacturers say, all of the reloading books say the same thing.
Whether or not a particular load is dangerous when substituting a different component, I would believe that if your load is near max, then it's a very good idea! And even if it isn't, you might find changing to a different primer caused fliers, that happened to me when substituting Federal Match small rifle from Remington 7 1/2's in my 222's. The Federals caused fliers! I do adhere to the practice of reworking if any component is changed, however after nearly a half a century of loading, my loads are pretty much set in stone.
Matt

[jmoore]

Something odd about small rifle BENCHREST primers is that they have thicker cups than regular small rifle primers. The compound is the same, though. SR primers are only rated to 40-45,000 psi whilst the benchrest are made for high intensity loads (small cases full o' powder) that ,although hot, are ballistically more uniform than your typical 80-90% loading densities.

Thus, if you change from, say, 7 1/2's to 6 1/2's pierced primers or excessively flattened primers often follow. Your load isn't hotter, its that the primer cup is thinner! I've learned a good deal of this the hard way, which led to doing a fair amount of research following my dramas. I always wondered why loading manuals are rather specific about the primers used, they just don't say why!