Spitfire Spring-Powered Nerf Shell is a fully 3D printable upgrade compatible with 40MAX blasters. No gas or rubber bands needed — just print, assemble, and add a common spring for reliable, powerful performance. Easy to print and assemble, this design offers a durable and fun mod for Nerf enthusiasts. Use responsibly — do not aim at people or animals. The designer is not liable for any damage or injury resulting from misuse. [https://youtu.be/bEucgPaS9To](https://youtu.be/bEucgPaS9To) [https://youtube.com/shorts/iNrx_C-okCw](https://youtube.com/shorts/iNrx_C-okCw)

Recommended to print with supports. Best results achieved using PLA Pro or PETG. Use a layer height of 0.2 mm and 20–30% infill for durability. Required spring: 5 kg force, wire diameter 1.5 mm, coil radius 25 mm, height 90 mm. Build guide: Assemble printed parts as shown in the reference images. Insert the spring carefully — one end may need to be slightly bent to fit securely into the designated hole. Make sure all parts move freely before use. No glue is required.  [https://youtu.be/bEucgPaS9To](https://youtu.be/bEucgPaS9To)