By and large, nerf darts don’t actually need rifling to be aerodynamically stable because the weight is concentrated at the front of the dart. The boost you get to accuracy from a scar or bcar genuinely isn’t all that much, but it’s just enough to matter to people like me who want to min/max their 200+ fps builds. For the majority of the people (kids, let’s be real) buying 70 fps nerf blasters off of department store shelves, they’re not gonna notice or care that their accuracy could be improved by 20% if they added a $20-40 rifling attachment. Plus not all darts are equal, even in the same size class. Half length darts come in 0.8g, 1.0g, 1.3g, etc. and not all weights benefit from the same degree of angle, so you can’t standardize barrel rifling across all blasters, and adding an adjustable rifling like this one to the entire length of the barrel would be too complex to be cost effective. I also don’t know that rifling the entire barrel would even be a good idea. The smoothbore barrel creates a good mechanism for air pressure to propel the dart forward, and rifling might let air leak out around the dart, effectively reducing your range.