Oh, dear (oy, ve?)
When skimming through the new posts, my twisted brain saw Mohel 12 instead of Molel 12. On reading the post, it seems I was not that far wrong
Even if the added length of the choke makes the barrel legal, the hassles and costs of winning that argument in court, should anyone in power think otherwise, are sure to outweigh getting a new barrel. An option could be having a competent smith weld the choke in place, making it permanent.