Numerous remixes of caliburn parts. My favorite is the katana magwell, followed by the chunky trigger guard. Found the normal one was too narrow, sharp, and generally uncomfortable while using, so I made a fatter, rounder one.
Also shortened the argus handguard, priming block, and made a short railgasm/argus combo to fit my shorter caliburn. i'm not sure how compatible that will be for other people though.
There's also a hella long muzzle to go over my 18" barrel that sticks out like 8" from the front. I used some mega dart foam to make sure it was centered at the very front