Federal Tax Stamp
All silencers and short barreled rifles require the purchase of a $200 Federal Tax Stamp.
The National Firearms Act (NFA) introduced in 1934 requires NFA firearms to be registered and taxed.
The $200 tax was quite prohibitive at the time, which was the goal of the National Firearms Act.
If adjusted for inflation, the $200 required in 1934 would be equivalent to $3,708.00 in 2017.