After 3 years of development, I'm now happy to be shooting the 3D printed #Liberator12k break-action shotgun.
There are still a few issues to address, but they have easy fixes.
1. Use a steel shaft collar to keep headspace.
2. Replace extractor with something chunkier.
Donate: bitcoin:172DaKThhFAA6Z8MFLpXUvSHE2UpjhXRXj