LockSleeve BCAR

This is the LockSleeve BCAR.

It's what I use for competitive matches, and I think it's pretty damn good.
It has two pieces: the Core, and the Sleeve. The Core has 6 "fingers" that sit around the barrel and are flexible. The Sleeve has ramps around its ID that push those fingers down against the barrel as you rotate the Sleeve around the Core. This causes the LockSleeve to very firmly lock itself into place and positively center it due to the rotational symmetry of the forces applied. It also doesn't need any hardware outside of the bearings and pins, so that's pretty cool.

It uses F683ZZ bearings - 3mmx7mmx3mm, and uses 3mm diameter pins to hold them in place. Any length from 10 to 16mm should work, but I usually use 12 or 14.

The original version is the 5x5 - a total of 25 bearings. If that's too many for you (I get it), there are also 3x3 versions available. I haven't tested them but they use the same geometry as other 3x3 BCARs I've made so I'm sure they'll be fine. The 5