Why is everyone paranoid about discussions involving manufacture of machineguns, machinegun parts, short barrelled long guns, and silencers?
The BATFE sometimes considers detailed discussion of those subjects to be illegal, or at least worthy of a pre-dawn raid. (They take machineguns the most seriously.) Naturally, most people don’t like being woken up by gun-toting black-clad ninjas, so the Forum discourages discussions of how to make machineguns, short-barrelled long guns, and silencers. Under federal law, you can legally make anything but a machinegun, but you must jump through hoops to do so. NFA Title 2 weapons are a complex subject, and W. Bardwell’s site (located on the main page of the Forum library) is a good resource for those who wish to know more.