I thought I needed (actually just wanted) a new set of .30-30 dies, so I bought a pretty red box of Hornady New Dimension dies. After sizing a batch of shells, I took them over to my L.E. Wilson case trimmer.
When I put the sized cases into the L.E. Wilson case holder, they were too small to be gripped by the holder. They literally rattled around in the case holder (yes, it was a case holder for sized cases and not fired cases...), so I could not trim them.
I cannot remember the numbers now, but they were sized considerably smaller than cases coming out of my ancient set of RCBS dies. Hornady customer service just said there was nothing wrong and their sizers are industry spec. I expected that. Rather than mess around with it, I went back to my RCBS sizer, but use the Hornady seating die. Problem solved in my case.
If you're wondering - there was nothing custom or different about the Hornady die. The set was a standard .30-30 set, and adjusted perfectly. I just got tired of trying to talk to Hornady about it, and since the RCBS-sized cases fit my rifles just fine, I'm good to go. Your own mileage may vary slightly. My RCBS set is from about the 1950s I think. passed down from the dad.