Daryl, thanks for the suggestions. I am pretty sure it is not a 6.5x55 because the 54 cartridges fit the magazine perfectly and appear to fit the bolt head perfectly. There is also only a normal, small, amount of resistance felt when the bolt is closed on a cartridge. The fired cases are not visibly the wrong shape, they are just stretched more than they should be. My understanding of what happens when a case is fired in a chamber that is slightly too large at the rear and also too long is that the firing pin whacks the case forward against the shoulder of the chamber, the powder ignites, gas pressure develops and expands the case to hold it forward and the rear of the case then expands/stretches back to the bolt face, thus creating the stretch marks a short distance ahead of the stronger web. If I understand the above process correctly, which I may not, then it appears to me that I have both a too large chamber and too much headspace.

I will try the idea of necking up and then down. I am also going to take the rifle to an old bench rest and Scheutzen gunsmith out at New Braunfels, Howard Dietz, and see if he has any ideas.

I have emailed Norma to ask them what gives with the too small/primer pockets. No answer yet.

Many thanks again for the suggestions.