Irrevocablability/Revocability only relates to whether the settlor can modify/revoke the trust after enactment. Modifying a trust relates to changing the provisions of the trust or completely revoking it, not a change in the assets owned by the trust. Hence, an irrevocable trust cannot be amended or revoked, but new assets can be placed into it and assets within it can be sold. If a firearm is placed in an irrevocable trust and later sold, all the sale proceeds must be put into the trust and, typically unless there is a provision stating otherwise, the trustee has a duty to invest those funds into another asset (firearm or otherwise) that will yield a good return for the beneficiary. The real benefit to a irrevocable trust is that the settlor's creditors (or soon to be X spouse) cannot attach to the assets of the trust. With a revocable trust, any creditor (including a soon to be X spouse) can attach to the assets in the trust because the settlor still has the power to revoke the trust.