For some extra loud fun during your next Nerf War, I've made a 3D printable Mega dart tip that let's you add cap gun caps to the tips of the Mega foam darts.
Print time @ 0.2mm w/support: about 20 minutes per piece
The assembly and testing video is available at: https://youtu.be/mOB03YSX-No
Disclaimer: While I've tested these tips quite a bit and the cap gun caps I'm using have never gone off when shot at a person, dropped on the ground, or even shot into a soft surface, it's still recommended that you DO NOT AIM AT PEOPLE OR ANIMALS.
The standard foam dart version is available at: https://www.thingiverse.com/thing:2241051