I really like Mighty Shrub's pivoting shell catcher on my Firefly so I remixed it for the Battle Axe by SillyButts.
Fits very nicely alongside my Battle Axe top rail shell holder:
https://www.printables.com/model/1074712-picatinny-silly-shell-carrier-x6-made-for-sillybut
In my experience so far it's been pretty easy to reload the Battle Axe magazine without pivoting the shell catcher out of the way (just rotate the blaster a little more towards you so you have clear access to the magazine), but it's also super easy to just lift-and-pivot the frame for reloads or to clear any jams.
The peg on the front support arm may need a little filing/cutting depending on your print tolerances. It should snap into its hole with minimal resistance, just enough to hold the frame in place while empty. The weight of the frame (especially with shells in the bag) is more than enough to keep it locked in place.
NOTE: Print the frame on its back (the inner side that faces the blaster) with supports in the channel the drawstring sits into. You want as sharp of an angle as possible so the drawstring can't escape.
I'm using a small mesh drawstring laundry bag for the catcher, but you can use a gallon ziplock bag and rubber bands in a pinch. I've been really liking this lace lock for securing the mesh bag in the drawstring grooves rock solid:
https://www.printables.com/model/585678-springless-lace-lock-parametric/files
Changes:
Changed the hinge arm geometry to fit the Battle Axe body
Modified the catcher frame's dimensions to accommodate the size of Silly Shells and the ejection travel of the Battle Axe blaster
Added a top shell deflector/bag support to make sure ejected shells make it through the window and into the bag
Added a forward support arm that goes on the front picatinny rail. Keeps the catcher from sagging/moving out of place when you run
The author remixed this model.
Changed the hinge arm geometry to fit the Battle Axe body
Modified the catcher frame's dimensions to accommodate the size of Silly Shells and the ejection travel of the Battle Axe blaster
Added a top shell deflector/bag support to make sure ejected shells make it through the window and into the bag
Added a forward support arm that goes on the front picatinny rail. Keeps the catcher from sagging/moving out of place when you run
NOTE: Print the frame on its back (the inner side that faces the blaster) with supports in the channel the drawstring sits into. You want as sharp of an angle as possible so the drawstring can't escape.