I'm fairly sure the answer to this question will be no because of the hardened steel, but I'm not a machinist so I will ask.
Can an existing die (.243 full length for example) be machined to change the shoulder angle to 40 degrees with perfect alignment at a reasonable cost, or is it best to just buy a new die?
Can an existing die (.243 full length for example) be machined to change the shoulder angle to 40 degrees with perfect alignment at a reasonable cost, or is it best to just buy a new die?