[lifeguard]

People will be sad when they realize the barrels are not rifled. That means these are plastic zip guns.

[xkcdfanboy]

It's not hard to add a rifling to the model is it? It seems like they are prototyping, testing, and incrementing designs.

[lifeguard]

It is impossible to add rifling to a plastic barrel that has metal projectiles fired through it at the speed of sound.

These are muskets.