When a 5 shot group has 4 under .5 min and one wanders an inch away. Shooting at 100 yrds with a 24 X scope, sand bagged, 1.5 lb trigger. After all else fails - examining neck tension. Neck sizing. Thinking of bushing dies, outer case trimming. But that doesn't compute with me. I was taught that its the expander plug that sets the final neck diameter. So why don't I hear discussion on expander plugs when ? And the chamber limits how much expansion the case can go to.