Thread: Fireform markings

I've just finished fireforming 100 Norma 300wsm cases into 7wsm (against best advice) and about half the cases have a very bright ring at the top of the web. Some also have a bright ring where the old body, shoulder junction was.

The 300wsm cases were sized so that the false shoulder in the neck set zero headspace and the projectiles were lightly jammed into the lands.

I've had case head separation before but that ring was much duller and wider than these rings.

I don't think it's a die mark because none of my Federal 7mm wsm cases have the marking.

To make matters more confusing I sectioned one of the worst offenders and there's absolutely no sign of thinning at the ring (of this case).

Anyone experienced anything like this? I'm gonna have to keep a very close eye on them.

Photo, the colour change above and below the line is also there, not just the camera