Thread: RCBS Dies... Problem?

I would say your new dies have a smaller body and base dimension than your old ones, this will cause tight sizing that last few mm as it is squeezin the whole body and base in smaller, this should make em chamber more easy but that brass has to go somewhere and it goes forward and pushes the shoulder forward, this should show as easy to chamber but hard or impossible to close bolt, check with vivid or some marker where the empty sized case is binding on the mouth/neck/shoulder and body.
Necks generally can be quite a bit longer than SAAMI spec in a SAAMI spec chamber but if that is the cause trim, if not then most likely the shoulder has moved forward, on the same case wind down an 1/8th of a turn until it will chamber with the slightest resistance on bolt closing=Zero headspace go down max 1/8th turn more and test another couple of brass and if all good you should be all set up, recheck for any sign of excesses case length.