This is a NERF barrel extension modeled after the HK MP5K sub-machine gun. (At least it's supposed to be the K) You can read more about it on Wikipedia: https://en.wikipedia.org/wiki/Heckler_%26_Koch_MP5#MP5K
This model is specifically designed to work with the NERF "Stryfe", but it should fit other models.
Also included is a model for a front-piece/guard. This piece slides onto the rail on the bottom of the barrel and mates up with the rail on the bottom of the Stryfe. I like using Talon2535's fore-grip handle with it: http://www.thingiverse.com/thing:815767
There is a "bayonet mount" ring mount that lets you connect it to some NERF blasters. "Twist-lock". Some trimming of the connector may be necessary. Or you may need to add a couple layers of masking tape to get a tight fit, depends on the blaster. DO NOT FORCE CONNECTION or you may break your NERF blaster.
The added length might increase the accuracy of your shots. But it might not.
I would love to get feedback from people.
Designed in OpenSCAD