What full length size (338 Lapua) to bump shoulder back slightly?

A neck die... No once-fired case will have grown to the point the shoulders need to be moved.

Hornady makes universal-for-caliber neck only dies that don't need a bushing. I have a 25 WSSM neck die that I use with whatever bushing I need.

After that point it's all about does the die work with your chamber. The cheaper the die the more likely not IMO. Will be cut to a minimum chamber spec and will tend to overwork brass unless you're lucky.
 

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