Approximately 6-9 months. The suppressor should arrive at your local FFL Dealer within a week or two then you will go in and complete the first form and submit it to the ATF and CLEO. You have to wait until that paperwork gets approved and comes back to the FFL Dealer before you can fill out the 4473 and take possession of your suppressor.
Years ago baffles inside a suppressor were made of rubber that actually rubbed the bullet as it traveled through the suppressor causing the bullet to slow down. With new innovations and precision manufacturing the tolerances in today suppressors are so tight now that rubber baffles are not needed. What we typically see is a 1-3% increase in muzzle velocity.
Typically a suppressor will lower your boom in the 25-40db range. A lot of factors play into decibel reduction like how long is your barrel, what ammunition are you using and are you using a bolt gun or a semiauto. Lowering your decibel 25-40 is significant.
No you do not need a class 3 to own a suppressor. The ATF must approve the transfer and it takes up to a year but it will be worth the wait.
A long as the states you are travelling to and through allow suppressor ownership you can travel with your suppressor. If a state on your route does not allow NFA items it is a good idea to get permission from the ATF before transporting your suppressor. Use Form 5320.20 to request permission.
When you travel with your suppressor — make sure you always have your tax stamp paperwork and your Trust if applicable.
States that currently allow private ownership of suppressors: AL, AK, AZ, AR, CO, CT, FL, GA, ID, IN, IA, KS, KY, LA, ME, MD, MI, MN, MS, MO, MT, NE, NV, NH, NM, NC, ND, OH, OK, OR, PA, SC, SD, TN, TX, UT, VT, VA, WA, WV, WI, WY