Make them yourself. As I recall you are the same chap who made a post about repeatability using a chucker a few weeks ago.
The back stop will just give you a fixed reference inside the chuck. I had to do the same thing with a run of parts many years ago but these were being run on a Jones & Lamson ATL. I loaded the parts by hand and ran the cycle. At the end of the cycle the chuck opened and I yanked it out and put in the new blank and held it while the chuck closed.
I have seen a screw machine that had an ejector pin that pushed through the chuck bore to spit the part out. It was cam operated just like the rest of the machine.
Which Acme machine do you have? I had the J&L that I could put 6" bar through the collet, a #3 and #5 Werner Swasy turret lathe, a Logan engine lathe and a small cam operated screw machine that used drum cams... can't recall who made it.
Hello, Thank you for the feed back. I have a RA Acme screw machine that was converted into a chucker, the machine is automation to load the parts and a cam open up the collect to eject the part into a chute. My problem seems to be when the part is loaded and the collect is closed the part seems to pull forward a little. Do you know if there is a difference in the way the collect closing on a bar machine to that of a chucker? If I make the backstops then how will the part eject?