I pulled out my standard steel (no carbide sizer) .45 LC die set yesterday to load up some rounds for my New Frontier .45. My set was by RCBS and dated 1977. Somewhere along the line I had picked up a Lee carbide sizing die to make life easier - I'm not sure how old the Lee die is.
I sized my cases with the Lee die and found that the cases were too large to grip a .451 bullet - they would slide in the cases with almost no interference. I checked the expander plug and it was .447 - obviously not the problem. OD of the cartridges sized in the Lee die were around .473 and cylinderical as expected from a carbide die.
I then tried sizing the cases with the orginal RCBS sizer die. The RCBS sized the mouth of cases down to approx. 467 with a slightly visible bottleneck for the last 1/4" or so - the diameter below the neck was around .473 like the Lee Sizer cases.
I didn't have time to size some more bullets to .4515 or .452 but I suspect the Lee sized cases will still be too large. I have a set of .454 and .460 dies but haven't tried sizing any cases in them yet.
Anyone else have similar experiences with the Lee or the "bottleneck" RCBS sizing die? I've used a lot of RCBS steel pistol dies in the past and continue to do so; perhaps I just didn't notice the bottlenecking?