I shoot one particular load from my 270 of 130g Interlocks with Ar2213 aka H4831.

The chronoed speed is a consistent 3070fps.

When I shoot that load in Win brass, no ejector marks, no sticky lift, nothing. When I shoot it in LC brass (necked down 30-06) I get these bright marks that correspond with the ejector slot. Again, no sticky lift, no flat primers, same speed on the chrono.

I can't work that out but I have concluded - right or wrong - that it's not excess pressure causing it.