[303carbine]

Originally Posted by Leeper

303 Carbine,
I think everbody on the thread knows what the hell you are talking about. However, not all are clear on the concept of maintaining or improving concentricity and the part the body portion of the die plays in this.
First, it is important to understand that no die can fix brass which in which the inside and outside is not co-axial. So, while the outside of the case may be perfectly straight, the inside will remain eccentric. When a case like this is sized in a die which does not support the body (like a 7 mag die sizing a 280, for instance), the neck is likely to be reduced further on the thin side and end up offset in comparison to the body. The same thing can occur in a piece of well-used brass which has work-hardened to a greater extent on one side. Now, in the first instance, the outside of the case neck ends up eccentric to the body but the inside may actually be close to concentric than it was before. I believe I can demonstrate this but I have work to do first. I will get back to it.
Good, concentric brass will allow the production of concentric ammunition much more easily; even with half-assed methodology. Crappy brass is likely to produce crappy ammunition regardless of the method or equipment used.
So, as long as the brass is good, the neck is likely to remain concentric, just as Rembo has stated. If the neck starts out eccentric, it will probably remain so although the point of eccentricity and the amount may change.
When all is said and done, whatever works does just that; it works. When I was a kid, I loaded ammo for my 303 using a 300 Savage sizer to neck size because that is what I had. This was used in a Lyman nutcracker tool. I seated bullets with a 30/06 seater in the same tool. While none of this was geared toward the production of precision ammo, it worked well enough for me. I could shoot good groups and shot a bunch of gophers with ammo loaded this way.
Your method of sizing 280 brass in the 7 mag die will serve you well and your brass life will be better than if you fl sized. Keep on shootin'. Leeper

The reason I used the 7 mag die to neck size 280 is the 280 neck sizer doesn't touch the case body, neither does the 7mag FL die. So, I can't see the difference in the neck sizing process.