Hi all,
I took the good work by mainblades and extended some capability. The major change was to replace the spring pin with a 3mm hole to use a screw to hold the spring. You can customize your slider in OpenSCAD by changing the bullet diameter and height. I also included an option to have a hollow body to speed print time and reduce filament usage. I just finished sizing over 1200 .45 ACP bullets using my slider, and it works great.

Update: A buddy of mine offered this modification (see picture #3)...instead of using a screw to hold the spring, he used a stiff wire bent into a loop for the spring, then pushed through and bent down on the other side. So if you don't have a screw handy, or change out the slider often, you can use stiff wire to make a loop.

Creality

Ender 3

No

Yes

.20

40%

I designed this to print upside down to reduce the number of supports required. Cleanup is easy, and installation even easier..