Where's that .002" difference?
Full length sizing dies for bottleneck cases have headspace. It's the distance from the die shoulder reference diameter to the bottom flat of the shell holder that's against the die bottom. The ones I've measured are universally about .005" less than the cartridge's rifle chamber headspace GO gauge. For example, 1.625" for 358/308/243 Winchester family cases.
They size fired cases' headspace back to about SAAMI minimum when the shell holder is against the die bottom per most die setup instructions. 308 cases end up with about 1.627" to 1.628" due to case brass spring back. That lets them chamber safely in SAAMI minimum spec chamber with 1.630" headspace with no more than about .003" head clearance.
Full length sizing dies for bottleneck cases have headspace. It's the distance from the die shoulder reference diameter to the bottom flat of the shell holder that's against the die bottom. The ones I've measured are universally about .005" less than the cartridge's rifle chamber headspace GO gauge. For example, 1.625" for 358/308/243 Winchester family cases.
They size fired cases' headspace back to about SAAMI minimum when the shell holder is against the die bottom per most die setup instructions. 308 cases end up with about 1.627" to 1.628" due to case brass spring back. That lets them chamber safely in SAAMI minimum spec chamber with 1.630" headspace with no more than about .003" head clearance.