I can only speak to swfa, and older leupolds, as that is what I have experience with. Swfa uses brass internal parts,and heavy duty erector springs. This allows precision, and longevity. As stated in other posts, my old leupolds had weak erector springs, and nylon internal parts. This caused poor return to zero, after a couple of hundred rounds. Night Force, uses brass internals,as I am sure some other good scope manufactures do. Those are the only 3 that I have torn apart ,or researched. Regardless of your choice,make sure the brands components are top notch.