I will be releasing an updated file set within the next week that will include the o-ring based parts. I will also be using clear plunger tubes as the standard from here forward.
I would also like to point out that I just printed the 100th Caliburn part set. By December I'm likely to have made more of these than I ever made of Longshot foregrip kits.
Edit: And now there's a body kit or derivative Caliburn product coming out soon from Argus Modworks.