I've been a user of RCBS dies lately until now.
I had a set of RCBS 44Mag dies that the sizing die was undersized and would not accept a case new or unfired. Returned it to RCBS and they replaced it with a carbide sizing die as the previous one had been steel only.
Bought a set of RCBS 6.5 Creedmoor dies that were scratching the sides of new cases and were also undersized. I would have to stand up to apply enough pressure to size the once fired brass with enough lube to get some shoulder dents. I sent the sizing die back to RCBS with a note about the two problems and received the same die back with a note "polished die". Using the dies again for the second time found that the scratches on the brass were gone but the sizing die was still under sized. Sent the dies (both) back to RCBS and told them this was the second time the same die had been returned and the sizing problem still existed. Losing my patience I told them to replace the set preferably with a carbide sizing die or keep the damn dies and don't send them back.
Haven't heard from them now after 11 days so I bought a set of Hornady dies for the 6.5 Creedmoor to go along with my other Hornady dies in 6.5 Grendel. I am through with RCBS dies going forward and loving the Hornady.
