I'd also like to add that I see post after post referring to what some "Hall of Fame" benchrest shooter does with his loads. Now that I've been around this thing for a decade, put on a few dozen events, and met several of these HoF types, here's my statement:
Not one of the HoF shooters got there by cleaning or not cleaning the inside of their case necks. Most of them couldn't spell concentricity, say nothing about check it. They did what made sense to them, found a load that shot "good enough" and then learned how to shoot it. Any HoF shooter I've witnessed at our matches would have become an HoF member shooting my loads, or Boyd's loads, or anybody's loads that were tailored to the gun.
What put them in the HoF is their competitive spirit, ability to read conditions and interpret what they say, and bench discipline. Lots of those HoF shooters were shooting loads that were put together on the hood of a pickup with a powder measure that hadn't been adjusted in 10 years and using a seating die they didn't even remember when they last set it. Their loads probably varied 3 tenths of grain on a good day, Lord only knows what the "concentricity" of the rounds were, and some of them, especially in the 6 PPC era, pounded the bolt shut with the palm of their hand because the cases had never been FL sized, never had the shoulder bumped more than occasionally.
Then they put the whole shebang into an old fixed front rest with a squeezey rear bag and proceeded to put 'em in little holes. Great stuff to watch.
New technology and practices have helped to overwhelm their older records, but even today I don't believe the top shooters are where they are because of their handloads. It's because of better barrels, better actions, better scopes, better rests ... but seldom because of cleaner case necks.