I was told by a national champion short range benchrest shooter that if the bullets were seated to the lands neck tension meant little to nothing. Is this true? From your statement above maybe not?? I always thought the case opened up before the bullet moved if loaded in the lands ?
He’s right about not seeing a difference, but you can also throw charges and “mushroom” with a hammer the start of a nail head on a bullet nose and an accurate rifle will still touch or one-hole that bullet with perfect ones - at short range.
But even at long range I think it’s still true that less-than-ridiculous neck tension differences don’t produce noticeable results.
I believe that greater neck tension just means the bullet hit the lands slightly faster, relatively reducing the pressure to engrave the bullet, such that the combined neck and barrel tend to counteract differences in neck tension, round to round.