Cs22,
Are you using the same manufacturer of brass? If not this might account for the variation in neck tension.
I use Lapua brass which has a consistent thickness of 0.013-0.0135" measured at four points of the compass around the mouth. Lapua is thicker than other brands. I use a Forster sizing die without the expander mandrel, so the outside of the neck is sized only. It imparts .003" of tension, measured by what the OD is after sizing and after seating. This is fine for an auto loader. If the bullets are moving on being loaded into battery they are not making any difference to group sizes.
The OD of the case neck is;
After sizing .2865
After seating, .2895
After firing, .2935
I don't anneal.
Are you using the same manufacturer of brass? If not this might account for the variation in neck tension.
I use Lapua brass which has a consistent thickness of 0.013-0.0135" measured at four points of the compass around the mouth. Lapua is thicker than other brands. I use a Forster sizing die without the expander mandrel, so the outside of the neck is sized only. It imparts .003" of tension, measured by what the OD is after sizing and after seating. This is fine for an auto loader. If the bullets are moving on being loaded into battery they are not making any difference to group sizes.
The OD of the case neck is;
After sizing .2865
After seating, .2895
After firing, .2935
I don't anneal.