Thread: Shoulder Bump Advice

Remove the expander then size a fired case and measure to the shoulder , if the case has grown its the die that's the problem . The problem is caused by the case body being sized and the shoulder not engaging the die .
If it only occurs with the expander fitted , lube the inside of the neck .

The former is the more difficult to correct , with rimless cases it's possible to have someone machine a few thou' off the bottom of the die , with rimmed magnums it would depend on the rim clearance within the die . Otherwise, its time to buy ,beg or borrow.
Don't try to reduce the shellholder, it may weaken it to the point of failure , leading to a stuck case .