This is the main document and it (along with the Certificate) must be signed by you and then acknowledged by a Notary Public. You will name someone to manage the trust at your death and name beneficiaries in the trust.
Any firearms not specifically left to a designated person can be held in the trust and/or sold by the successor Trustee (the proceeds of any sales are added to the remainder of the Trust); when the trust no longer owns any restricted firearms the trust is distributed to the remainder beneficiaries.
Geographic Distribution of NFA Applications for Processing by ATF
Transfers of National Firearms Act Firearms in Decedents’ Estates