I was been recommended a load for 6PPC that involves federal 250m primers though at the moment I only have CCI benchrest primers, a case of 1000.

How much difference can they make, and are the CCI's superior? Does the fact that they have "benchrest" written on the package mean they are among the most accurate primers availiable?

I am not a benchrest shooter, though I would like to develop a round for varminting so accuracy is fairly important.

Take a look at the www.castingstuff.com web site. On the bottom of the opening page is a primer testing page. It might answer some of your questions. The CCI BR primers were some of the best. web page

Load 'm. I use nothing but WSR's. Just work up your load with that primer. FWIW, Dutch.

A lot of benchrest shooters use the CCI BR primers. They believe that the CCI BR primers are made with harder metal cups than other brands. Due to the elevated presures they operate the 6ppc's at, it is an advantage in preventing the primer from piercing or extruding into the firing pin hole.