ATF worksheet 4999. I am sure some have objectively run their points on this. A length greater than 26” would make the weapon a SBR. ATF did three example weapons at the end, two of three were declared SBR. I don’t see how barrel length of 11.5 is meeting the length of 26” or less.
I believe I can link to federal register:
https://www.federalregister.gov/docu...ilizing-braces