I'll do my best to explain.....
1. First go to and open the Parts Generator.....then click on the right tab which says, "Collator Plate Generator." You should see the picture below:
2. Then on the right under "Orientation", pick "Base Down Brass Plate."
3. Under "Caliber", pick "Large Pistol." (below that you'll see red print....that describes how to preview your plate...go ahead and preview it before you make the height change......then "X" out of that and get back to the previous screen.)
4. Then on the LEFT side it lists the parameters for the plate design.....first one says caliber 15....second one says Collator_Plate... 8. That second one means the plate will print 8 millimeters high.....a .357 case is 32mm high! Too low for a tall wobbly case....so change that # to 16 as shown in my illustration....it'll work MUCH better! Now preview it again and it should look like the picture below:
Notice the next to the last parameter..... should say, "collator_Plate....180" This time it's Plate diameter and 180 is the normal size plate which is plenty big for pistol bullets.....if you want it for 300 size or Mongo base, you'll need to change that number.
Then just save to a .STL by pressing "Gen" next to where you did the previews......make your G-code file, and print.
.357/.38 wasn't included in TylerR's list of plates because he doesn't shoot that....so he wouldn't want to print one for it.
You will also want to print a brass slide and drop tube....and a short plug for the normal bullet drop hole. Somewhere is a brass slide that doesn't have the opening adjustable....it's just wide open. You can use the adjustable one, but use the tightening screw to hold it wide open or you will not drop them fast enough not to hang.
Food for thought......You really can choose the "small pistol" rather than "large pistol" as the holes in the small one are 12mm diameter and the large one's holes are 15mm. But what I found is that sometimes longer cases get hung up, when they don't drop fast enough....IOW's a smaller hole's trailing edge may beat the long case to the edge of the drop hole.....leaving you with the choice to slow it down to a crawl. The 15mm hole doesn't seem to cause problems and that edge doesn't come as fast. I suppose if 2 cases doubled together you might have a problem, but I just haven't seen that. But nothing wrong with trying the small pistol size, but why if the large one works.....and you can also use it for .45. IOW's why print 3 plates when one or two work for what you shoot.