This box will hold 100 .22LR rounds. The insert sits down into the box on a lip and the lid slides into the grooves. Pull the lid back one row at a time to dump out just what you need. I have also included a photo of a cross-section that I printed for testing purposes so you can see how everything sits within the case. The box measures 166mm long x 46mm wide x 32mm tall.
I have added a second, smaller version of this ammo case that holds 20 rounds instead of 100. The files are marked _x20 so... enjoy :)
I have uploaded a version of the sliding lid that is 0.3mm thicker. The original was just a little too thin after it is slid back and forth a few times. Use whichever is right for you, depending on your printer.
Another Sketchup Model - Debunking the Myth that Sketchup is Useless in 3D Printing
Due to the design of the sliding lid, the use of supports is unfortunately unavoidable. You will need supports enabled everywhere. I used 0.3mm Support Z Distance and 0.8mm XY Support Distance. Oddly enough, there was little, if any support material at all, but the ridges printed perfectly. Without supports enabled at all, these same ridges failed, so...