This is an old thread, but there was an interesting thread on the Cast Boolets forum with some information and a picture of the mythologic 50 BMG Star. As stated earlier, the author confirmed that it was built by John Powers and thought that only three were built. He is the owner of one. He also has a Star Rifle Machine. How lucky can you get!!!! I have suggested that he join the forum.
The picture which was "lifted" from the Cast Boolets forum shows a standard Star Universal, a Star Rifle machine, and the 50 BMG Machine
I too was trying to get this Cast Boolits member to join here. For posterity, and with his permission, I am posting his account / history of that Star-like 50 BMG reloader:
"...Jon Powers is one of the best machinists I have ever met. He is or was at Willis Tool in Michigan. He developed a .44 Magnum and .45 Colt gas-operated semiauto pistol that looked like an enlarged Colt Woodsman and was a thing of beauty. He made several (how many, I don't know, I think it was maybe a dozen) and sold the patent to IMI which came out with the clunky Desert Eagle (with a TERRIBLY wrong grip angle). John tested one of his Magmatics to destruction and could not blow it up with smokeless powder. He finally did it in with a 240 grain bullet loaded into a case charged with 20 or so grains of ditching dynamite.
In the late '70s and early '80s, after seeing the custom .50 BMG rifles I built for myself and Kent Lomont, he got the .50 bug and scratch built his own falling block .50 BMG rifle. Upon seeing Kent's and my Star Progressive reloaders and our Dillon RL1000 (which didn't work as well as it should have due to less-than-Star machining tolerances), he designed and built a .50 BMG progressive press for himself. Kent and I fell in love with it and persuaded him to build one for each of us. I don't know if he ever made more of them--to my knowledge there were only the three made. I heard John's was stolen(!) and Kent's went through a shop fire about 25 years ago, but Jon rebuilt it. Mine is still as good as the day I received it.
The size of the case makes sizing brass fired in an M2 a bit difficult, so I first size the brass (and then trim it) on a single stage press if I'm using cases from a machine gun. But for cases fired in my bolt guns, it runs like a greased clock doing all steps at once.
I lost touch with Jon about 10 years ago, around the time I had my stroke and got divorced. Hope he's doing well..."