Printed using .27 layer height, 25% infill, 1 shell. Using Replicator 5.5 but with default speeds (printing small objects like this with acceleration I find melts the previous layer too much). Printed with full support, it's only required to support the inside of the bowl.

I've printed this a few times a few of them had plastic "hairs" preventing BB flow.. a drill bit of the correct size cleared that up.

Pull the spring loaded trigger and insert tool, position the tool so the BB's do not flow into the gun. Fill it to the top and take out any remaining BB's (top BB sticks out about 2mm). Tip the butt end of the gun down at about a 60 degree angle, move the loader to the front of the gun - BB's should drop right in.

Original Tinkercad object:
tinkercad.com/things/bMy319N45M0-daisy-powerline-15xt-bb-loader

I noticed a minor issue with my grouping/"holes" on tinkercad, it produced an indent in the half circle support. Please use the "fixed" STL. Tinkercad is updated