This is a 22lr ammo box with a sliding lid with a detent. I designed it to take CCI style 50 round trays, because I don't really like the cardboard their standard rounds come in.
I printed it with 3 walls and 20% infill and it works fine for me.
Attention: You might want to look into my newer version here https://www.printables.com/model/415732-sturdier-22lr-ammo-box-with-sliding-lid. It has lots of improvements over this one!
The author marked this model as their own original creation.