Just looked at their position (2011) and for now it seems there's no issue. However, since the entire question wasn't ruled on in Thompson Center (1992), it remains possible that future BATF positions may change.
No matter really for me, was mostly curious, and long ago decided the Hand Rifle wasn't my cup of tea. A 12" Contender is about the most I'd want to futz with, and 10" better yet.
Thanks,
