This is basically a mashup of the Wildstyle front shell carriage with a Thumper harmonica clip, to enable the Thumper to fire Silly Shells
Here it is firing Corvus 9x short dart Silly Shell - https://www.printables.com/model/1291745-silly-shell-9x-short-darts-airtight-barrels-3x3-sh
Here it is firing Demolisher rockets using the post attachment
The clips are compatible with the existing Thumper harmonica clips so you can mix and match
Should be printed with supports pictured below :

UPDATE 26/9/2025 : Added a ‘Captive’ clip (Thumper - Silly Shell clip - Captive-NoAdvance v3.stl) which doesn't advance the clip stack. The shell carriage is also looser and a bit more forward, which makes it easier to manually reload
Used by itself (turning the Thumper into a WildStyle basically), or as the last clip in your stack.
This allows you to fire off all your clips, and still be able to manually reload shells and continue firing.
Check out my other parts for the Thumper! - https://www.printables.com/@JoonChor/collections/2652758
The author remixed this model.
Mashup of a Thumper harmonica clip with a Wildstyle shell carriage, to enable the Thumper to fire Silly Shells