To some extent, I agree with what Leo said. Years ago, one of my technicians competed at the Original Pennsylvania 1,000-yard Benchrest Club and loaded his ammo with standard RCBS dies so I never bought into paying extra for a micrometer adjustable seating die. All of my rifles, and I load for probably 20 calibers, shoot well under one MOA groups with many capable of even better like these recent two from a .22-250 REM.
Consistent exact powder charges are key as is a primer that ignites all the powder and at the same point in the barrel. For that reason, I use magnum primers in some non-magnum cases with powders for which magnum primers are not usually recommended, like these 6.5-.284 Normas.
The now-discontinued IMR4007SSC is not a powder for which magnum primers are required but they made the load more consistently accurate and since I was not near a maximum powder charge, there was no danger in trying the hotter primer.
Ed