I couldn't find a gel blaster thread adapter that was strong enough to withstand use in battle so I remixed a design by And219y and reinforced it to be a bit stronger. I still highly recommend using a strong material like ABS, ASA, PA, PC, or any alternatives the ensure the adapter doesn't snap and printing at 100% infill is a must. I printed it with the wider end facing down and it seemed to print well with no supports although a brim might be necessary. I've only tested this design on 2L bottles so far but should work on any bottles with the same thread.
Gel_Blaster_Adapter.stl | 5.6MB |