https://jeffersonoutdoor.com/contact-us/
To get on their waiting list just use the contact page on their site. In the comment just ask them to add you to their email list for whatever bottom metal you want.
I have mine cut at 16.5” and love how handy it is. If it were me I would figure out how far you plan on hunting and determine your barrel length based on the velocity you need to reach that distance. My .223 is for practice and my kids to hunt with so I don’t plan on letting them take shots...
Same thing happened to me when I had my Tikka Cerakoted. Mine actually fired on a live round when I first closed my bolt after getting it Cerakoted. When I tore it apart the trigger housing was completely loose.
Now I disassemble my guns myself before I get it Cerakoted or the barrel...