From
http://www.silencertalk.com/legality.htm , The following states allow ownership of silencers: AL, AR, AK, AZ, CO, CT, FL, GA, ID, IN, KY, LA, ME, MD, MS, MT, NE, ND, NV, NH, NM, NC, OH, OK, OR, PA, SC, SD, TN, TX, UT, VA, WA, WV, WI, and WY. Of the sixteen states which do not allow civilian ownership, CA, IA, KS, MA, MO, and MI allow Class-3 dealers and Class-2 manufacturers to own silencers.
My home state of WA allows ownership, but bans use. So I only get to enjoy my silencers when I travel out of state.
You can down load ATF forms from
http://www.titleii.com or order them from the ATF. Your local sheriff has to sign the ATF form 1 or 4 unless you use a trust to own the silencer for you. You also need to send in the forms with your mug shots, fingerprints and form 5330.20 attesting to your US citizenship. Approval takes 1-2 months, but I heard it is taking a bit longer now as the ATF has been flooded with applications since Obama was elected.
I learned how to operate a lathe when making a silencer for my 300 whisper. After making seven of them the only hard part (or best part) is thinking of a better design to try next. The best forums for info on silencers are
http://www.subguns.com and
http://www.silencertalk.com .
Ranb