Re: Concentricity gage?
This is an old thread but one that is pretty important and after spending an entire week playing with a concentricity guage, I decided to add my two cents. I just got a new toy, a 7MM best of the west rifle with a stiler action. I bought 150 pieces of new brass and set out loading up the best , most accurate load possible. Question. Does new brass need resized prior to loading? It is so undersize that sizing it is a waste of time. First shot with new brass will fire form it to fit exactly in your chamber. Now check case length and trim to correct length. Some pieces had streached .025 and were .015 too long! All case necks were nearly perfectly round and concentric after firing and after resizing. Problem was most of the loaded bullets necks were within .002 but the bullets were .006 to .008 out of round . When checked close to the neck and out near the tip, the rounout was nearly the same. The bullets were straight and the problem was the thickness of the case wall not being even. The solution that I used for these was to mark the high side and place the cartriges in the gun with the mark up. This alone cut groups in half. After firing, I turned the necks to get the thickness the same all the way around. After resizing and firing again the bullets lined up much better and group size was down to 5/8 inch at 200 yards.Sometimes that little extra cost for better brass would save time and money in the long run. Cheap brass, especially specials on brass should be avoided or at least measured before purchasing.
The idea of pushing the bullet back to straight will only work if the bullet is crooked. Measure close to neck and near the tip, if they are close to the same ,check wall thickness. The little things do make a difference!
Phil Conklin.... Shooting Instructor for The Best of the West