I want to build a non SBR 629 clone with a middy barrel so there is no space between the moderator and the FSB. I think it lends a more authentic look. The faux 4.5" moderator "BRICK" makes has 1" of threading that when silver soldered to a cut down (12.5") middy barrel gives me my NFA free 16" barrel.

So will a 12.5" barrel cycle this thing? I don't want to sleeve the moderator over the barrel unless I have too.