Shell With Fixed Diameter

The diameter on the original design was .5 mm too narrow for my gun (20 mm vs 20.5). i don't know if its the same for others, but here's my version (of the 12 mm dart diameter) where that's fixed. The 12 mm dart version was giving me problems originally with the dart having too good of a seal in the shell and being unable to fire, but i think that the fixed fit has given it a better seal with the plunger tube; so that's fixed by this as well.

(here's a speedloader i made for this thing as well: https://www.thingiverse.com/thing:4858167 )