7mm mag case issue

[whit]

I went to shot a ladder yesterday and decided to shot an old round to check my scope before shooting a ladder test. My first 2 shots were 6 inches higher than where they should have been. The velocity on my chrono was in line with what I had recorded previously so I chalked it up to the scope getting bounced around while hunting and readjusted the scope. The remaining shots fell into a group right were I wanted them. The photo is the case from the first shot. Any idea of the cause of the denting of the shoulder? The only thing I could think of was residual oil in the chamber not allowing even expansion of the case.

Sent from my SM-G970U using Tapatalk

 

[1Shot]

This can happen with a load that is too light or powder that did not get lit good. Just a reminder ALWAYS remove all oil from a chamber and bore before a shot. Leaving any oil can result in ruining your rifle. Bullet pushes oil before it until the bullet pushes past it and when it does I will form a hydro ring or bulge in the bore. Same can happen in the chamber between case and chamber wall.