Hello, I have a few questions around concentricity and neck turning and how those work together. Concentricity: What is this? Can you please explain how this guage works, it's value in a factory remington sendero in 7mm Mag? Neck Turning: I am confused on do you turn/trim the outside or the inside of the neck? Recommendations on brand/model? Value in doing this? What is the right thickness of the neck for a 7mm Mag? I pretty much do everything else on my loads but never went down this road. Looking to tighten groups up a bit. I currently shoot 160 accubond, nosler brass, cci mag primer, IMR4350 at 60.5g and new OAL 3.365 (used to be 3.343 but after 500 rounds got a bit of throat erosion and I think I need to move up). I shoot about .7 inch groups at 100.