Welshshooter,
A minimal shoulder bump is best; .002" average is good. Die instructions ensure sized cases will fit SAAMI minimum chamber specs; about 98.7654321% of the time.
If you can control sized case headspace to a .001" spread, then bump shoulders back only .001". You'll need to have the bolt face squared up first else the case heads' out of square issues won't allow consistent grad clearance. Head clearance is the space between bolt face and case head when the firing pin has pushed the case full forward in the chamber before the round fires. Too much head clearance allows more case body stretching when fired. Too little can bind the closed bolt and it won't be in battery exactly the same for every shot.
Out of square case heads and bolt faces cause horizontal shot stringing when two lug bolts are in battery and the lugs are at 12 and 6 o'clock. 1/4 to 1/2 MOA horizontal stringing is common. It's caused by the bore axis wiggling horizontally as the bullet leaves the barrel caused by horizontal flexing of the receiver.
PS:
My 7th great grandfather in my Dad's lineage was born in the southernmost extent of Wales, in the Glamorganshire region. He came to what's now Jamestown, VA, in 1673. The acreage he claimed is now a parking lot in a shopping center.