If a Gun Trust Lawyer® provided your gun trust, it will not require a tax return. As stated in the instructions memorandum that comes with every NFA Gun Trust from a Gun Trust Lawyer®, the trust is a disregarded entity and any transactions that create a gain or loss pass though to the individuals. This does not mean that transactions that take place are not taxable but it would be treated the same as if you bought and sold items as an individual. This may be more complicated with a multi-settlor trust and you should discuss the specifics of this with your accountant or CPA to determine how to properly report the income on the individual settlors tax returns.
If you have another trust that was not prepared by a Gun Trust Lawyer®, you should ask an attorney or CPA about the taxable issues as while many trusts will be treated the same for tax purposes, your trust may be different and require a tax return or other federal or state documents to be filed.