MRB-5 Mega Launching BCAR

The MRB-5 is a BCAR (bearing centered auto rotation) for hobbyist dart blasters (Nerf) that allows the user to front load and fire mega darts while providing stabilization and an accuracy boost while firing normal half darts. It is meant to provide a cost effective BCAR solution that also allows you to launch mega darts, which are utilized in certain gamemodes for shield breaking and other functions. This BCAR will fit onto any standard 13mm ID barrel, found on almost every hobby design.

The BCAR utilizes 9 bearings in a 3x3 arrangement and has an angle of 5°, providing decent stabilization for most blasters around the 175-250fps range. 

The Mega launching portion is rifled, utilizing the rifling found on Silly Shells. FPS of the launched Mega dart depends heavily on your blaster's PT volume and spring, but on my APX-24 DMR that hits 220FPS using half darts I was able to achieve an average of about 100FPS on Mega.

This has been a long term project of mine. Initially it started off as a normal Silly PCAR modded to launch Mega, but as I required something more high FPS, this was developed. This is like the 4th iteration of this idea, so its been a lot of trial and error to get it to work as well as it does. A lot of time went into tweaking the bearing dimensions and positioning and the mega launching portion. I am not sure its as good as some of the higher end BCARs on the market, but it definetly is cheaper.

Parts List

• 9x F683ZZ bearings
• 9x M3x8mm BHCS 
• 1x 016 O-ring
• 1x M3x4mm SHCS (optional)
• 1x M3 heatset insert (optional)

Assembly

Insert the bearings into the slots and fasten into place using the M3x8mm BHCS. Make sure the flanges on the bearings face up towards the top of the cap screws! Slide the rear part onto the barrel first, then the 016 o-ring, and then the front part with the bearings installed. Screw both parts together until it is tight on the barrel. 

To optionally lock the BCAR onto the barrel to prevent it from rotating, utilize the optional heatset insert and M3x4mm SHCS. Install the insert using a soldering iron and screw the SHCS in to lock the rear part of the body in place in your barrel. WARNING: SCREWING INTO THE BARREL TOO HARD WILL POTENTIALLY DAMAGE YOUR BARREL AND/OR LEAVE VISIBLE MARKS.

3D Printing

3D print the body at the smallest layer height available, recommended 0.08mm. The locking collet can be printed at 0.2mm layer height. 5 walls and 50% infill for everything. In testing, this was strong enough to survive hours of abuse and competitive use. I still wouldn't drop your blaster muzzle-side down from a high height, though…

NONE of my files are to be used or sold by Frontline Foam, by downloading my files, you agree that you are not Frontline Foam and/or related to Frontline Foam or Derrikk Sun.

Utilizes a Silly-derived o-ring collet system and is based off of my previous Mega-Modded PCAR, itself a derivative of the Silly Spigot PCAR. Mega dart rifling is taken from the rifled mega dart Silly shell.