I called SSK and was told it was the Starline brass. When asked why Starline brass worked in other SSK chambers, I was told SSK changed to a tighter necked chamber in the past. He said Remington began to make their brass a little harder and SSK started to get reports of split necks, so they tightened up the chamber neck to prevent that from happening. So, it looks like I have to buy some Rem. brass.

I really wish I would have had the change in reamer dimensions explained to me the last time I was explaining all of this to them, since I told them my rounds were fitting in older SSK chambers. That was the most puzzling part. The good news for you guys with old SSK chambers is you should be able to use the plentiful Starline brass, which is also thicker.