My primary hobby during high school was to modify Nerf guns to improve the firing range and even made many Nerf guns from scratch. Pictured below are some of the Nerf guns that I modified or built.

The lancer, a Nerf Longshot modified to include an angel brass breech, reinforced priming mechanism, stronger spring, and a working toy chainsaw attachment.

This Nerf gun was never built, but it was a 3D CAD model I designed in SolidWorks as a learning exercise.

PETG barrel doomsayer. It has 12 barrels and is pump action.

Plusbow cut from polycarbonate with a skirt seal.

Pump-action rainbow made from clear pvc with a skirt seal.

PVC Snap rifle with neoprene washer seal and clothespin trigger.

PVC Bow.