Nerf Apollo Picatinny lower rail

The [Nerf Rival Apollo](https://amzn.to/2TOEHSi) is a solid springer. If you don't already have an Apollo, you're probably better off buying a [Helios](https://amzn.to/2MfFiKh) It seems to have all the positives of the Apollo as well as a several improvements.

That trapezoidal orange piece in front of the finger guard appears to be decorative. This part replaces it with a functional picatinny rail useful for attaching a swiveling fore-grip.