Here's an article I wrote on die setup and shoulder bump last year that might help. The Sinclair Hex Bullet Comparator I used is designed for measuring OAL to the ogive, but by using a larger caliber hole than the cartridge you're loading for lets it seat down on the shoulder of the case to measure shoulder bump. Since the nut I have only has holes up to .30cal it only works on cartridges up to 6.5mm, but it's easy enough to make your own by purchasing a 1" nut (on the flats) and drilling the appropriately sized hole(s) into one of the flats to meet your needs. Sinclair also offers a second version for .17, .20, .224, .277, .308 and .338 calibers that will allow you to do up to .30 cal cartridges.
http://www.savageshooters.com/content.php?476-Sizing-Die-Setup-and-Shoulder-Bump
