Silencers are legal for private ownership in AL, AR, AK, AZ, CO, CT, FL, GA, ID, IN, KS, KY, LA, ME, MI, MD, MO, MS, MT, NE, NV, NH, NM, NC, ND, OH, OK, OR, PA, SC, SD, TN, TX, UT, VA, WA, WV, WI, and WY. They may be owned by Class 3 dealers and Class 2 manufacturers (but not individuals) in: CA, IA and MA. Territorial law prohibits possession in the Territories and Possessions of the United States.
Civilian silencer possession is prohibited in CA, DE, HI, IA, IL, MA, MN, NY, NJ, RI and VT. WA recently amended their code to allow use. The MI AG wrote an opinon declaring the ATF registration forms a defacto license allowing unlicensed civilians own them. MO recently amended the law to allow civilians to own them also. MN recently allowed a bill to die in committee that would have allowed the DNR to use silencers.
All legally possessed silencers are registered with the feds, including those owned by the government. Some ban silencer unless they are registered with the feds. TX bans civilian ownership, but registration is an affirmative defense to prosecution, so the ATF authorizes transfer there. VT has a $25 fine for silencer possession, so naturally the ATF will not allow them in that state.
Only those people who import, manufacture or deal in silencer (and other title ii firearms) need an FFL/SOT class 1, 2 or 3. The FFL is $200 for three years and the SOT is a minimum of $500 a year. Manufacturers also pay the 2250/year ITAR.
There is no license required to own, make buy or sell silencers. For unlicensed persons they are transferred on the ATF form 4, made on the ATF form 1, and tax free transferred to heirs or other organizations on the ATF form 5. The transfer tax is $200 whenever the silencer is transferred to or from an unlicensed person unless it is on the ATF form 5. The ATF routinely authorizes transfers to anyone who fills out the forms correctly. I have never heard of anyone being denied unless they screwed up the forms. Unless the entity receiving the silencer is a corporation or trust, the person receiving the silencer has to obtain the signature of the local sheriff on the back of the application, then send it in along with two fingerprint cards, two passport sized photos and form 5330.20. If a mistake is made in the application, it is sent back along with a letter describing what needs to be fixed. If the transfer or making does not happen, then a refund of the $200 can be applied for.
A sale only needs to go through a dealer if it crosses state lines. A person has to be at least 21 years old to buy from a dealer, at least 18 to make or buy from an unlicensed person in the same state. A person can sell their silencer (one they made or bought), the same $200 tax is paid, and two taxes are paid if it crosses state lines. One when it goes to your state’s dealer, then another when transferred to the buyer in the other state. This means there is little market for used silencers.
Due to the strict controls placed on silencer in the USA compared to other countries where they are controlled less and the $200 tax, people want an effective durable silencer. Since they are not a common mass produced firearm, the price is high; from $150 to $3500.
Silencers only reduce muzzle blast noise. They do nothing for action, bullet flight, and impact noise just as a car muffle does nothing for engine, tire, wind and transmission noise. They typically reduce noise by about 20 to 40 decibels. OSHA recommends hearing protection for noise more than 84 decibels, some industry experts recommend hearing protection for short duration impulse noise from firearms greater than 140 decibels. Here is a link to some silencer test results, but it is about 5 years old and obsolete.
http://www.silencertests.com/results.htm . Depending on the firearm and silencer combination used, ear plugs may still be required to prevent hearing loss.
I make silencers as a hobby and learned to operate a lathe while making my first silencer. It is a great way to beat the high cost of buying them.
Ranb