Originally Posted by indiansumer
Just want to make sure I have this right....I'm loading a .300 RUM. Before resizing my i.d. is also .310. After resizing it is .304. My Berger 210VLD's measure .308. Will this give me enough neck tension? I see that JE Custom said he would shoot for .300 or .008 less than the bullet. I just figured that the size of the expander ball on the RCBS FL die was giving me the proper size and neck tension.
Inside neck diameter is difficult to measure accurately unless you have special gauges. Caliper blades are flat and shouldn't be used to measure concave surfaces. Outside neck measurements will be fine.
How much neck tension is NEEDED? - IMO about .002" of neck tension is adequate for most hunting rifles. BR guys often use less and autoloading rifles would benefit by more. Either way, .002"-.003" is a good range. More tension isn't really going to hurt anything except the life of the overworked necks. However, .008" would require much more setting pressure than I would like.