I've shot 15-shot test groups at 1000 yards with my prone rifle using brand new Winchester brass in 30 caliber magnums that are equal to or smaller than benchrest records. The only way I've resized them to equal what they do when first fired is to full length size them then size just the body with a special die that reduces the pressure ridge right in front of the belt back down to about new case diameters. Never got decent accuracy by neck only or partial FL sizing of belted cases. Nothing wrong with Winchester brass in 7 mag's either; sort it to 2 or 3 grain spreads in case weight; no need to prep/true primer pockets or flash holes. Turn the necks if they've got more than half a thousandths thickness spread.