Materials used in the construction and manufacturer of supressors varies as to what caliber supressor you are making.
Aluminum, machineable delrin, carbon steel, stainless steel and titanium may be used.
NOTE ON LAWS:
If it is a legally registered supressor in your home state, you may shoot it anywhere it is legal to discharge a firearm. NO state has a law that a range must call law enforcement if they see one. If one desires to fire a supressor on a public range, it is best to let them know in advance and be prepared to show them a copy of the registration papers to prove its registered.
This also lets the RO put any inquiring shooter to rest , that they are aware of it and it IS Legal. Somebody may call 911 when they see it so always have a copy of NFA paperwork with you when firing NFA weapons.
You may consider letting the fire it...and instantly win a new friend !
To some, NFA supressors and machineguns are pornography...to me just a day at the range.