I wasn't clear when I described what I do--sorry about that.
I bought as a spare part the press ram that fits the RCBS Reloader Special press. You have to order the retainer spring with it--don't ask how I found that out. And it will require a bit of trimming and fitting, nothing radical--but like a Ruger BH they come in semi-finished/kit form.
Assembly completed, I snap the proper expander into the ram, and use that unit like a center-punch. I sit the check on a chunk of 2" x 4" scrap lumber, center the tool in the check cup, and give it a tap with the rawhide mallet. About half the time, the checks fall free; when they don't, I use a played-out common screwdriver blade to prompt them off. I can do 4-10 per minute, depending upon how motivated I become and how interesting the ball game becomes on the shop TV. I am so darn spoiled, but most of us here have known that for 2 decades.
IME, you don't need to fully spread the check's cup to have the (e.g.) Hornady or gator check fit easily onto a Lyman casting's check shank. A light tap gives enough spread to ease fitment.