25cal. Carbide Expander Mandrel (.256")

I purchased this to expand 6mm Remington brass (current production by Hornady) from 24 to 25 caliber as the first step in getting it to 6.5 caliber. Forming a wildcat from 6mm Remington parent case. I was previously using an old Sinclair expander mandrel and die. The PMA mandrel dropped into the Sinclair die body perfectly, so I didn't have to re-buy that part. The Sinclair product was falling pretty badly, and causing run-out on the necks to be problematic. I would have to apply a small amount of pressure, release, turn the case in the shell holder maybe 30 degrees and go again, over and over until the expander broke completely through the neck. The 6mm Remington has a long neck, so it took a few minutes. Pressing harder in fewer steps resulted in the neck being slightly bent one way creating an insurmountable lack of concentricity. The final step is accomplished with a Hornady 6.5 Creedmoor neck die running the expander ball in just far enough to break through the neck into the case body. There is only about .003" of runout to play with, and Hornady brass isn't THE most concentric in the world to start with. It seems adequate in this lot, however. I have not used the PMA expander enough to know if it will gall like the Sinclair, but I was able to make the following observations: First, there was no difference in the amount of work required to successfully expand the 6mm brass to the new diameter. It still took several passes spinning the cade a little at a time. Probably the same amount as it took with the Sinclair. However, what I found was that after finishing the cases having used the PMA carbide expander first, was that run-out actually DECREASED slightly from that of the original parent case! Sometimes this is seen when full-length sizing, but never in my experience of case forming where the neck size is increased. This may be because of the extra lubricity of the carbide and me just not perceiving a difference between it and the old Sinclair stainless model. The Hornady neck sizer is used like the .256 expander in that the ram is run up with the case only far enough to feel a good resistance, then backed off and the case turned in the shell holder on the sizing press. I do use dry lubricant (graphite) on the necks prior to beginning. I also used it with the Sinclair attempts. If it's producing better brass than I started with, how can it be bad? It isn't as good as if I had a dedicated expander of about .249 or .250" to use as a first step, then this one next, and the 6.5 last. That would, I believe, greatly speed up the process. But this one is tapered up to .256 from about .22 caliber starting point. The transition is just too abrupt to expand the neck fully without distributing the force evenly around the neck. I'll keep looking for a custom expander size, but until then, I am content in knowing that I'm actually creating more accurate brass than I started with!