Nerf Rapidstrike Battery Door Holder Retainer
Save those thumbscrews!* This attaches where the barrel extension would normally go, and holds the battery door well in place.
*You may wish to keep a screw handy if you don't trust the print that well.
Disregard the supports in the photo; I left them on so I can anneal the part later. Supports are there to preserve the bump which ensures a tight lock; feel free to remove it and flip the object 180° if not wanted.
Future revisions may involve strengthening the entire tab that extends from the cylinder. This thing still needs battle testing!