5xR BCAR

This is the 5xR BCAR, the culmination of all my past BCAR work.

I use this as a no-compromise BCAR for competitive games, incorporating design elements from past works, commercially available BCARs and imput from competitive players for the ultimate BCAR.

Features of the 5xR BCAR include: very good venting with no freebore, a sleeve and nut that can be printed in a separate color while maintaining an orange tip, a bearing stack spacing that maximizes contact while not being so close as to weaken the overall structure, a “lined up” row of bearings that traces out a rifling groove on contact with the dart, and a bearing count divisible by 10. 

My biggest gripe with most home-made BCARs is the uneven number of bearings needed, since the uxcell F683ZZ bearings are sold in packs of 10, and common bearing orientations (9, 12, 15, 16, 18, or 25 bearings) leave you with extra or too few bearings. This design ensures you use every bearing so extra packs of bearings are unnecessary, and you won't have extras to keep track of.

This BCAR also has a significant (~10) FPS drop, so blasters will need to be tuned up to meet the desired performance. This can also work to dampen an overpowered blaster to meet an FPS cap, which can come in handy. 

I have not tested every geometry and every combination. The 5x4, 8 degree BCAR works wonders at 150, and should work up to ~250 fps. The 5x6, 5 degree BCAR works well at ~270 FPS. The the 4.2 degree BCAR works at 300+ FPS. These are extremely accurate and are very capable BCARs.

Printing and Assembly

Print the BCAR body muzzle down without support. The the threads should be facing up. 

The 4-stack sleeve fits all the 5x4 models, and the 6 stack sleeve fits all the 5x6 models. Print the sleeve with the keyed side on the baseplate.

The 4 stack BCARs use 20 F683ZZ (3mm x 7mm x 3mm) flanged bearings (2 packs) and 20 M3x16mm grub screws. 

The 6 stack BCARs use 30 F683ZZ (3mm x 7mm x 3mm) flanged bearings (3 packs) and 30 m3x16mm grub screws. 

M3x14mm screws are preferred, but any longer than M3x16mm and the sleeve will not fit. Grub screws allow one to recover the bearings, and they don't have the tolerance and fitment issues the M3x14mm pins did.

A -016 O-ring (or any one that fits) is used to lock the BCAR down to the barrel. Slip the nut onto the barrel, followed by the O-ring and then the BCAR itself. The nut geometry is shared with the Silly Spigot and Chance's Covered BCAR.

The 5x4 8 degree long BCAR is a lengthened 5x4 that uses the 5x6 sleeve. The length is cosmetic, but the BCAR works normally.